ACUS01 KWNS 281253
SWODY1
SPC AC 281252

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0752 AM CDT Wed Aug 28 2024

Valid 281300Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE OHIO
VALLEY TO THE NORTHERN MID-ATLANTIC COAST...AND ACROSS PARTS OF
NORTH AND SOUTH DAKOTA...

...SUMMARY...
Severe thunderstorms are expected from the Ohio Valley to the
northern Mid-Atlantic Coast, and across parts of North and South
Dakota.

...Synopsis...
In mid/upper levels, a progressive northern-stream pattern will
prevail through the period, with the main feature being a cyclone
now apparent in moisture-channel imagery near the southeastern
corner of BC. The associated 500-mb low should move eastward
roughly along, or just north of, the international border through
the period, with the accompanying trough extending south-
southwestward. By 00Z, the low should be near the southwestern
corner of SK, with trough to northern UT. By 12Z, the low should
reach extreme south-central SK, with trough across central MT to
southwestern WY.

Downstream, a complex but much lower-amplitude shortwave trough was
evident over Lake Superior and adjoining portions of ON and western
U.P. of MI. One part of this perturbation should break eastward to
the St. Lawrence Valley by the end of the period, while the trailing
part drifts eastward over Lake Superior and the U.P. Of perhaps
greater direct influence on convective potential, an MCV was
apparent in composited radar imagery over southeastern IA. The
associated perturbation should move across much of central IL today,
reaching western OH by 12Z tomorrow.

The 11Z surface analysis showed a cold front from northern ME west- southwestward across Lake Ontario and southern Lower MI, becoming quasistationary for the time being across southern parts of Lake
Michigan and WI, to northeastern NE, then a warm front over
southwestern SD, to a low over southeastern MT. This front is
expected to move southeastward by 00Z to coastal NS, Cape Cod, Long
Island, northern parts of MD/WV, and southern parts of OH/IN/IL,
becoming a diffuse warm front northwestward over central IA,
southwestern MN and central ND. There it will be overtaken by
another cold front -- initially analyzed through the low over
eastern MT and across northwestern WY. By 00Z, this second,
stronger cold front should extend from central ND across central/
southwestern SD to east-central WY. By 12Z, the western cold front
should extend from a low over southeastern ND or northeastern SD
across south-central SD, western NE and northeastern CO.

...Ohio Valley to Mid-Atlantic...
Widely scattered to scattered thunderstorms are expected along and
south of the front today from IN to the Mid-Atlantic Coast, and
perhaps the southern New England Coast/Long Island vicinity.
Damaging gusts and isolated large hail will be possible.

Coverage of convection is uncertain, but relative concentrations may
develop downshear from what is now disorganized/nonsevere convection
over OH (in the same UVV field), and ahead of the MCV over parts of
IL/IN, becoming organized across parts of IN/OH. Diurnal heating of
a favorably moist airmass is expected to weaken already modest
ambient MLCINH along the outlook corridor by late morning. With
lift along the front and prefrontal outflow/differential-heating
boundaries, growth of morning to early afternoon development into
one or more complexes appears to be a plausible scenario, rendering
a greater wind than hail threat. Surface dewpoints commonly in the
mid 60s to low 70s F will offset modest mid/upper-level lapse rates
enough to contribute to peak/preconvective MLCAPE in the 800-1500
J/kg range from OH eastward, and 1000-2000 J/kg back into portions
of IN. Weak, generally veered low/middle-level flow will limit
vertical shear. Still, nearly unidirectional westerly flow through
a deep layer will foster movement of convection parallel to the
low-level moisture-instability axis.

...Dakotas...
A line or arc of scattered thunderstorms should develop along/near
the cold front during late afternoon into evening, perhaps initially
over ND where deep-layer forcing will be stronger, then southward
into greater capping in SD, as the front impinges on greater
moisture and lingering boundary-layer instability.

Ahead of the cold front, enough easterly component to near-surface
flow will develop to support moist advection into the convective
genesis zone, with surface dewpoints into the 60s F becoming common.
Capping at the base of a modest EML will suppress development for
much of the afternoon, especially over SD, but once frontal lift
overcomes it, a corridor of 2000-3000 J/kg MLCAPE should be
available southwest of (and parallel to) the warm front. Though the
strongest flow aloft and large-scale ascent will remain behind the
cold front, the eastern rim of stronger height falls will spread
over the frontal zone, with enough mass response to both foster
favorable vertical shear for supercells and enhanced storm-relative
flow in low levels. Effective-shear magnitudes of 30-40 kt (locally
higher) and broad low-level hodographs along and south of the warm
front should foster supercell development, until mergers and upscale
growth occur. Large to very large hail and severe gusts will be the
main concerns, though a tornado is possible. However, relatively
weak midlevel flow may encourage a transition to messier, quasi-
linear mode with embedded LEWP/bow formations for a few hours.
Activity should weaken overnight as it moves into stabilizing
boundary-layer air, though a 45-55-kt LLJ may encourage persistence
of a cluster or two tonight into the eastern Dakotas.

..Edwards/Bentley.. 08/28/2024

$$

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ACUS01 KWNS 281638
SWODY1
SPC AC 281636

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1136 AM CDT Wed Aug 28 2024

Valid 281630Z - 291200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
NORTH DAKOTA/SOUTH DAKOTA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
MIDWEST/OHIO VALLEY TO MID-ATLANTIC...

...SUMMARY...
Severe thunderstorms are expected across parts of the Dakotas and
from the Ohio Valley to the Mid-Atlantic Coast.

...Dakotas...
Have upgraded portions of south-central North Dakota/north-central
South Dakota to a categorical Enhanced Risk for what should be a
relatively greater likelihood and concentration of severe storms
late this afternoon through early/mid-evening.

A prominent upper-level trough centered over western Montana and
southern Alberta will continue generally eastward over the Canadian
Prairies and toward the northern High Plains, with a
trough-preceding/basal upper-level jet resulting in considerably
strengthening southwesterly winds aloft by peak heating into
tonight. This will be atop an increasingly moist boundary layer
(dewpoints increasing through the 60s F) ahead of a surface low
across South Dakota and a front extending northward into North
Dakota.

Thunderstorms should develop near the front by late afternoon/early
evening, perhaps initially across North Dakota where overall forcing
will be greater, and subsequently southward into South Dakota where
richer low-level moisture and greater buoyancy will reside. Given
steep lapse rates and the reservoir of instability, these initial
storms should be supercells capable of very large hail amidst
strengthening flow aloft. Large to very large hail and severe wind
gusts will be the most common hazards, although a tornado risk may
also exist particularly across north-central South Dakota/far
south-central North Dakota near the surface low/warm front-related
triple point where moisture/low-level SRH will be maximized. Over
time, relatively weak mid-level flow may encourage a transition to
messier, quasi-linear modes with embedded LEWP/bow formations for a
few hours. Activity should weaken overnight as it moves into
stabilizing boundary-layer air, though a 45-55-kt low-level jet may
encourage persistence of a cluster or two tonight into the eastern
Dakotas.

...Midwest/Ohio Valley to Mid-Atlantic States...
Widely scattered to scattered thunderstorms will pose a risk for
damaging winds particularly mid/late afternoon through
early/mid-evening regionally. Some hail may also occur on a more
marginal and isolated basis. This severe risk will primarily span
parts of Indiana/Ohio eastward to the coastal Mid-Atlantic/Delmarva
vicinity, although the overall extent and magnitude of today's risk
is still a bit uncertain.

The boundary layer will not be overly moist by late-summer
standards, particularly across the middle Ohio River Valley, but a
relatively richer moist axis (through the lowest 2-3 km AGL) extends
this morning from the upper Ohio Valley eastward toward the coastal Mid-Atlantic/Northeast. The boundary layer will also not be overly
unstable later today, with severe-adequate MLCAPE generally limited
to 2000 J/kg MLCAPE.

Aside from differential heating related to last night's convection
across the Midwest, several impetuses for thunderstorm development
to the south of the primary Great Lakes front may include the
eastward transitions of MCVs across southeast Lower Michigan and
north-central Illinois, which should be influential into the Lake
Ontario/New York/northern Pennsylvania and lower/middle Ohio Valley
vicinities, respectively, later this afternoon and evening.
Effective shear will tend to be limited to 20-25 kt, but slowly-increasing-with-height deep-layer westerlies will support multicell-related damaging wind/some hail potential as low-level
lapse rates steepen and the boundary layer moderately destabilizes
this afternoon.

..Guyer/Wendt.. 08/28/2024

$$

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ACUS01 KWNS 281951
SWODY1
SPC AC 281949

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0249 PM CDT Wed Aug 28 2024

Valid 282000Z - 291200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ALONG THE NORTH
DAKOTA SOUTH DAKOTA BORDER...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN PLAINS AND THE OHIO VALLEY INTO THE MID ATLANTIC...

...SUMMARY...
Severe thunderstorms are expected across parts of the Dakotas and
from the Ohio Valley to the Mid-Atlantic Coast this afternoon
through this evening.

...20z Update...
No substantial changes have been made to the prior outlook. Storm
coverage should gradually increase over parts of the OH Valley and
Mid Atlantic through this afternoon. Damaging gusts will be possible
with the stronger clusters of storms, potentially focused from
eastern OH into WV and PA.

To the west, supercell development is expected near the surface low
and along the trialing surface trough/wind shift across western
SD/ND late this afternoon. Moderate mid-level ascent overspreading a
warming and moistening air mass across the Dakotas will allow for
rapid storm development and intensification as CINH is removed.
Large hail remains the primary threat, along with damaging gusts,
given strong buoyancy and robust supercell wind profiles. However,
strong low-level turning may support a risk for a couple of
tornadoes with the more discrete supercells, especially near the
warm front. Most short-term guidance does show gradual upscale
growth this evening and into the early overnight period across the
eastern Dakotas. Should this occur, the risk for damaging winds may
increase with the greater organized/persistent clusters before they
move into more stable air across parts of western MN. See the prior
discussion for additional information.

..Lyons.. 08/28/2024

.PREV DISCUSSION... /ISSUED 1136 AM CDT Wed Aug 28 2024/

...Dakotas...
Have upgraded portions of south-central North Dakota/north-central
South Dakota to a categorical Enhanced Risk for what should be a
relatively greater likelihood and concentration of severe storms
late this afternoon through early/mid-evening.

A prominent upper-level trough centered over western Montana and
southern Alberta will continue generally eastward over the Canadian
Prairies and toward the northern High Plains, with a
trough-preceding/basal upper-level jet resulting in considerably
strengthening southwesterly winds aloft by peak heating into
tonight. This will be atop an increasingly moist boundary layer
(dewpoints increasing through the 60s F) ahead of a surface low
across South Dakota and a front extending northward into North
Dakota.

Thunderstorms should develop near the front by late afternoon/early
evening, perhaps initially across North Dakota where overall forcing
will be greater, and subsequently southward into South Dakota where
richer low-level moisture and greater buoyancy will reside. Given
steep lapse rates and the reservoir of instability, these initial
storms should be supercells capable of very large hail amidst
strengthening flow aloft. Large to very large hail and severe wind
gusts will be the most common hazards, although a tornado risk may
also exist particularly across north-central South Dakota/far
south-central North Dakota near the surface low/warm front-related
triple point where moisture/low-level SRH will be maximized. Over
time, relatively weak mid-level flow may encourage a transition to
messier, quasi-linear modes with embedded LEWP/bow formations for a
few hours. Activity should weaken overnight as it moves into
stabilizing boundary-layer air, though a 45-55-kt low-level jet may
encourage persistence of a cluster or two tonight into the eastern
Dakotas.

...Midwest/Ohio Valley to Mid-Atlantic States...
Widely scattered to scattered thunderstorms will pose a risk for
damaging winds particularly mid/late afternoon through
early/mid-evening regionally. Some hail may also occur on a more
marginal and isolated basis. This severe risk will primarily span
parts of Indiana/Ohio eastward to the coastal Mid-Atlantic/Delmarva
vicinity, although the overall extent and magnitude of today's risk
is still a bit uncertain.

The boundary layer will not be overly moist by late-summer
standards, particularly across the middle Ohio River Valley, but a
relatively richer moist axis (through the lowest 2-3 km AGL) extends
this morning from the upper Ohio Valley eastward toward the coastal Mid-Atlantic/Northeast. The boundary layer will also not be overly
unstable later today, with severe-adequate MLCAPE generally limited
to 2000 J/kg MLCAPE.

Aside from differential heating related to last night's convection
across the Midwest, several impetuses for thunderstorm development
to the south of the primary Great Lakes front may include the
eastward transitions of MCVs across southeast Lower Michigan and
north-central Illinois, which should be influential into the Lake
Ontario/New York/northern Pennsylvania and lower/middle Ohio Valley
vicinities, respectively, later this afternoon and evening.
Effective shear will tend to be limited to 20-25 kt, but slowly-increasing-with-height deep-layer westerlies will support multicell-related damaging wind/some hail potential as low-level
lapse rates steepen and the boundary layer moderately destabilizes
this afternoon.

$$

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ACUS01 KWNS 290046
SWODY1
SPC AC 290044

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0744 PM CDT Wed Aug 28 2024

Valid 290100Z - 291200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE DAKOTAS...

...SUMMARY...
Severe thunderstorm threat continues across parts of the Dakotas
this evening.

...01z Update...

Strong mid-level short-wave trough is well evident in satellite
imagery, extending from the AB/SK border, south into eastern ID.
This feature will shift into eastern MT/WY by the end of the period
as a 70kt+ 500mb speed max translates across western ND into
southwest MB. Scattered supercells have developed ahead of this
short wave from near Minot ND to just north of Mobridge SD. Latest
model guidance suggests a weak surface low, or at least a wave, will
track northeast along the surface front into southeast ND by 29/12z.
Over the next few hours, LLJ will increase across the eastern
Dakotas and this should encourage eastward propagation of convection
within a concentrated zone of low-level warm advection. Latest
diagnostic data suggests ongoing storms are rooted within the main
corridor of instability, and peak updraft intensity may linger
through 03-04z before a more hostile environment is encountered
downstream. Very large hail may be noted for the next hour or two,
along with some risk for a tornado, then hail/wind threat will
linger into the late-evening hours.

..Darrow.. 08/29/2024

$$

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ACUS01 KWNS 290546
SWODY1
SPC AC 290545

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1245 AM CDT Thu Aug 29 2024

Valid 291200Z - 301200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE UPPER/MIDDLE MISSISSIPPI VALLEY...

...SUMMARY...
Severe thunderstorms are expected across the Upper/Middle
Mississippi Valley to the central Plains. A few severe storms also
will be possible over portions of the mid-Atlantic region.

...Upper/Middle Mississippi Valley...

Southern portions of a strong upper trough, currently located over
the northern Rockies, will eject across the Dakotas this afternoon.
As 70-80kt 500mb speed max translates through the base of the trough
across ND, primary upper low will track across southern AB into
northwestern ON during the latter half of the period. Latest model
guidance suggests very strong 12hr mid-level height falls just north
of the international border, with more modest falls into the upper
Mississippi Valley by 29/00z.

Strong low-level warm advection will likely prove instrumental in
one or more thunderstorm clusters over eastern ND/northwestern MN at
the start of the period. LLJ responsible for this activity will
shift into northwestern ON during the day, and this warm-advection
activity should lift north of the border as well. However, strong boundary-layer heating will occur across eastern NE into extreme
southwest MN by early afternoon. This will aid instability, and CINH
will begin to weaken along the front, as surface temperatures rise
into the mid 80s across central MN. NAM forecast sounding for KLJF
at 22z is thermodynamically impressive with MLCAPE around 5400 J/kg
and 0-6km shear approaching 30kt. 30-35kt deep-layer shear is
expected along the northern extent of the stronger buoyancy. As a
result, supercells are expected to develop along/ahead of the cold
front, supported aloft by the upstream short wave. Large hail,
severe gusts, and a few tornadoes are the expected hazards with
these storms.

Scattered convection, with a more-isolated severe threat, is
forecast along the trailing cold front across the central Plains as
readings breach convective temperatures later in the afternoon. Wind
profiles at lower latitudes are not very strong, so this activity
will be multicellular and less organized. Even so, some risk for
hail/wind can be expected into the evening hours.

...Middle Atlantic Region...

Dominant surface anticyclone over southeastern Canada will shift
across ON/QC, which will allow a synoptic front to drape itself
across the Middle Atlantic during the afternoon. This boundary will
focus scattered thunderstorms as convective temperatures are
breached by mid afternoon. Wind profiles favor mostly disorganized pulse-multicell updrafts. These storms will move slowly southeast
with an attendant risk for wind and perhaps some hail. Robust
updrafts will be strongly diurnally driven.

..Darrow/Jirak.. 08/29/2024

$$

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ACUS01 KWNS 291251
SWODY1
SPC AC 291249

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0749 AM CDT Thu Aug 29 2024

Valid 291300Z - 301200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE UPPER MISSISSIPPI VALLEY REGION...

...SUMMARY...
Severe thunderstorms are most probable this afternoon and evening
over portions of the upper Mississippi Valley region, with a threat
for tornadoes, damaging to severe gusts, and sporadic large hail.

...Synopsis...
The mid/upper-level pattern will be characterized by a progressive
belt of westerlies across the northern tier of states, and messy
area of ridging across the south-central/southeastern CONUS,
suffused with numerous small vorticity maxima and a few slow-moving
MCVs. In that northern stream, a strong shortwave trough -- with
embedded closed cyclone now located over extreme southern SK -- will
move eastward to southern MB and the Dakotas by 00Z. The trough
should deamplify overnight and eject northeastward to
northwesternmost ON by 12Z, while a positively tilted trailing
portion of the trough lingers across parts of WI/IA/NE/KS. Farther
east, a weak perturbation -- evident in moisture-channel imagery
from just north of Lake Huron in ON to astern Lake Superior -- will
weaken gradually and move southeastward across the remainder of ON
to NY and New England by the end of the period. An even weaker
shortwave trough -- initially extending from central OH across
southern IN -- should move slowly southeastward into the central
Appalachians.

At the surface, 11Z analysis showed a triple-point low over
northeastern SD, with a warm front southeastward over southwestern
MN and northern IA, becoming quasistationary to a weak cold front
over central IL, southern IN, central OH, central PA , and NJ. The
eastern part of the front should drift southward over the Mid-
Atlantic through the period, while the western part proceeds
northeastward across MN/WI as a warm front. A cold front was drawn
from the low southwestward over west-central NE and east-central CO.
By 00Z, the cold front should reach northern/central MN,
northwestern IA, eastern NE, north-central/southwestern KS, and
parts of southeastern CO/northeastern NM. By 12Z, the front should
extend across parts of Lake Superior, WI, northern/western MO,
southeastern KS, northern/western OK, northwest TX, and southeastern
NM.

...Upper Mississippi Valley to central Plains...
Scattered thunderstorms should develop along/ahead of the surface
cold front -- earliest (around midday) where deep-layer lift is
strongest over northern/central MN, then later where stronger
capping, weaker upper support, but stronger heating will be present
from around the Missouri Valley southwestward. All severe hazards
will be possible with greatest vertical shear supporting a threat of
supercells in MN and perhaps northern IA for the first few hours of
the convective cycle. If supercells can remain discrete/mature long
enough before the quasi-linear evolution occurs, tornado potential
could be relatively maximized over central MN where the overlap of
large buoyancy, low LCL and greatest SRH is forecast. Activity
overall should evolve into a line of numerous thunderstorms by late
afternoon and evening, with severe gusts and marginal hail becoming
the dominant concerns. Convection should weaken over eastern and
southern parts of the "marginal area tonight, while moving into a less-unstable, larger-CINH airmass from WI to southern KS.

Although the main mid/upper cyclone/trough will be pivoting
northeastward over Canada, the southeastern rim of associated height
falls and mass response will pass across the "slight risk" outlook
area. This should back the near-surface flow ahead of the front
enough to enlarge low-level hodographs and shear vectors, and to
strengthen effective-shear magnitudes into the 30-40-kt range
(decreasing southward over IA). A deep troposphere, rich boundary-
layer moisture with dewpoints commonly in the upper 60s to low 70s
F, and steep low-level lapse rates, should support MLCAPE commonly
in the 2500-3500 J/kg range, and locally nearing 5000 J/kg, within
the northward-narrowing warm sector, over IA/MN part of the outlook.
Farther southwest, buoyancy will weaken due to somewhat less
moisture content and greater boundary-layer mixing.

...VA/NC to southern PA...
Scattered multicell thunderstorms are expected to form this
afternoon along and south of the front over the outlook area,
offering isolated gusts near severe limits and marginally severe
hail. This activity will develop in a plume of rich low-level
moisture, with lower-elevation surface dewpoints in the upper 60s to
low 70s F. That, along with diurnal heating offsetting modest
midlevel lapse rates, should support MLCAPE in the 2000-3000 J/kg
range. Weak deep-layer flow/shear should keep activity relatively disorganized, with pulse severe possible.

..Edwards/Bentley.. 08/29/2024

$$

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ACUS01 KWNS 291648
SWODY1
SPC AC 291647

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1147 AM CDT Thu Aug 29 2024

Valid 291630Z - 301200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
MINNESOTA AND WESTERN WISCONSIN...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
MID-ATLANTIC REGION...

...SUMMARY...
Severe thunderstorms are expected this afternoon and evening over
portions of the Upper Midwest, with a threat for tornadoes, damaging
winds, and sporadic large hail, especially across parts of Minnesota
into western Wisconsin. Other severe storms are expected across the
central Plains and Mid-Atlantic/Carolinas.

...Upper Midwest/Central Plains...
Have upgraded portions of central/eastern Minnesota into western
Wisconsin to Enhanced Risk for a perceived greater aggregate severe
risk, highlighted by a transition to an increased damaging wind
potential by evening.

An upper-level trough will continue generally east-northeastward
from southern Saskatchewan toward Manitoba and eventually far
northwest Ontario late tonight, with southern-peripheral height
falls and moderately strong southwesterly winds aloft as far south
as the far eastern Dakotas and Minnesota into Wisconsin. Scattered
thunderstorm development is expected by mid-afternoon along the
front from northern Minnesota south-southwestward into southwest
Minnesota and the central Plains including eastern/southern Nebraska
into northwest Kansas.

The most severe-favorable ingredients are expected across
central/southern Minnesota, where 2500-3500 J/kg MLCAPE will
coincide with 30-40 kt effective shear. Some initial supercells can
be expected with large hail. Tornado potential should be maximized
across central Minnesota and possibly far western Wisconsin in
vicinity of a weak surface wave/warm front-related triple point,
where low-level moisture/SRH will be maximized, somewhat analogous
to the South Dakota/North Dakota border vicinity yesterday late
afternoon and early evening. Storms should otherwise steadily grow
upscale by early evening, with storm mergers leading to quasi-linear
segments and possible bows with an increased damaging wind potential
across Iowa, and especially eastern Minnesota into western
Wisconsin.

...Carolinas/Mid-Atlantic including parts Virginia/Pennsylvania...
Scattered multicell thunderstorms are expected to form this
afternoon, offering isolated damaging wind gusts and marginally
severe hail. This activity will develop in a plume of rich low-level
moisture, with lower-elevation surface dewpoints in the upper 60s to
low 70s F. That, along with diurnal heating offsetting modest
mid-level lapse rates, should support MLCAPE in the 2000-3000 J/kg
range.

..Guyer/Jewell.. 08/29/2024

$$

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ACUS01 KWNS 291956
SWODY1
SPC AC 291954

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0254 PM CDT Thu Aug 29 2024

Valid 292000Z - 301200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
MINNESOTA AND WESTERN WISCONSIN...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE UPPER MIDWEST AS WELL AS THE MID ATLANTIC....

...SUMMARY...
Severe thunderstorms are expected this afternoon and evening over
portions of the Upper Midwest, with a threat for tornadoes, damaging
winds, and sporadic large hail, especially across parts of Minnesota
into western Wisconsin. Other severe storms are expected across the
central Plains and Mid-Atlantic/Carolinas.

...20z Update...
Minimal changes were made to the prior outlook. Thunder
probabilities have been lowered across western parts of the central
Plains behind the cold front. An isolated severe storm will be
possible ahead of the front from the central Plains southward into
the southern High Plains. Moderate buoyancy is supporting a fair
amount of convection with some potential for damaging outflow winds
or marginally severe hail. However, weaker deep-layer shear and
modest large-scale ascent should keep the threat minimal prior to
frontal passage later tonight.

Across parts of the upper MS Valley and Midwest will maintain the
Level 2/3 Slight/Enhanced as is. Scattered storms are ongoing and
expected to increase in coverage through the afternoon and into this
evening. Increasing deep-layer shear and partial heating ahead of
the bands of storms near the cold front should allow for more
robust/organized storms to gradually develop through the remainder
of the afternoon. With the expected convective coverage, storm mode
is trending toward more linear solutions, though moderate deep-layer
shear and strong low-level turning with height may support a few
embedded or semi-discrete supercell structures. Damaging winds are
the primary threat, but occasional large hail and a couple of
tornadoes are possible, especially near the warm front with any of
the more persistent rotating features.

Across the central Appalachians and Mid Atlantic, no changes were
made to the severe risk area. The predominate hazard remains a few
multi-cell clusters capable of damaging wind gusts. Convection
ongoing over the higher terrain in western VA/PA and WV should
gradually expand eastward, with some potential for consolidating
outflow. See the prior outlook for more information.

..Lyons.. 08/29/2024

.PREV DISCUSSION... /ISSUED 1147 AM CDT Thu Aug 29 2024/

...Upper Midwest/Central Plains...
Have upgraded portions of central/eastern Minnesota into western
Wisconsin to Enhanced Risk for a perceived greater aggregate severe
risk, highlighted by a transition to an increased damaging wind
potential by evening.

An upper-level trough will continue generally east-northeastward
from southern Saskatchewan toward Manitoba and eventually far
northwest Ontario late tonight, with southern-peripheral height
falls and moderately strong southwesterly winds aloft as far south
as the far eastern Dakotas and Minnesota into Wisconsin. Scattered
thunderstorm development is expected by mid-afternoon along the
front from northern Minnesota south-southwestward into southwest
Minnesota and the central Plains including eastern/southern Nebraska
into northwest Kansas.

The most severe-favorable ingredients are expected across
central/southern Minnesota, where 2500-3500 J/kg MLCAPE will
coincide with 30-40 kt effective shear. Some initial supercells can
be expected with large hail. Tornado potential should be maximized
across central Minnesota and possibly far western Wisconsin in
vicinity of a weak surface wave/warm front-related triple point,
where low-level moisture/SRH will be maximized, somewhat analogous
to the South Dakota/North Dakota border vicinity yesterday late
afternoon and early evening. Storms should otherwise steadily grow
upscale by early evening, with storm mergers leading to quasi-linear
segments and possible bows with an increased damaging wind potential
across Iowa, and especially eastern Minnesota into western
Wisconsin.

...Carolinas/Mid-Atlantic including parts Virginia/Pennsylvania...
Scattered multicell thunderstorms are expected to form this
afternoon, offering isolated damaging wind gusts and marginally
severe hail. This activity will develop in a plume of rich low-level
moisture, with lower-elevation surface dewpoints in the upper 60s to
low 70s F. That, along with diurnal heating offsetting modest
mid-level lapse rates, should support MLCAPE in the 2000-3000 J/kg
range.

$$

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ACUS01 KWNS 300048
SWODY1
SPC AC 300047

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0747 PM CDT Thu Aug 29 2024

Valid 300100Z - 301200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE UPPER
MIDWEST...

...SUMMARY...
Thunderstorms, a few severe, will spread across the Upper Midwest
this evening. Some risk for isolated wind/hail persists through
about 04-05z.

...01z Update...

Strong, well-defined upper low is lifting northeast across southern
MB early this evening. Trailing trough extends across the eastern
Dakotas with the southern most portion affecting western KS. This
feature is largely responsible for an elongated band of convection
across the Upper Midwest, arcing ahead of a synoptic front into the
central Plains. The most organized portion of this linear MCS is
advancing across western WI/southeast MN/IA. LLJ will shift east
across IA/WI this evening, suggesting this activity will remain
organized for several hours. Most supercell structures have been
disorganized along the line, and damaging winds will likely be the
primary severe threat, as large hail has been mostly absent with
this convection.

Scattered-numerous thunderstorm clusters persist across the Middle
Atlantic region this evening. 00z soundings from this region exhibit
modest lapse rates, but seasonally high PW values. Wind profiles are
marginally supportive of organized updrafts so this activity has
likely peaked in intensity. Aside from an isolated damaging
wind/hail report, the overall severe threat should gradually
diminish over the next few hours.

..Darrow.. 08/30/2024

$$

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ACUS01 KWNS 300544
SWODY1
SPC AC 300542

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1242 AM CDT Fri Aug 30 2024

Valid 301200Z - 311200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
SOUTHEAST LOWER MICHIGAN...

...SUMMARY...
Scattered strong to severe storms are possible across eastern lower
Michigan later today, with more isolated strong/severe storms into
parts of the Midwest, and also across parts of the Carolinas and
Virginia into northeast Georgia.

...Great Lakes/Midwest Region...

Strong upper low, currently located over MB, will shift into
northwest ON by the start of the period. Notable short-wave trough
will advance from the upper MS Valley at 18z into the central Great
Lakes by 31/12z. At the surface, synoptic front will advance into
Lower MI-central IL-central OK by late afternoon. This boundary will
serve as the focus for potential robust convection, especially as
surface temperatures warm into the mid 80s. NAM forecast sounding
for KDTW at 20z exhibits negligible CINH, with MLCAPE on the order
of 2400 J/kg, though 0-6km bulk shear is seasonally weak. Deep-layer
flow will increase a bit into the early evening hours, so updraft
organization should be more favorable by this time. Even so,
forecast lapse rates are marginal and this may limit overall
severity. Southern extent of large-scale support should aid
convective development ahead of the front. Some risk for wind/hail
will exist with this activity.

...Southeast/Southern Middle Atlantic...

Weak deep-layer flow will be noted across the southern Middle
Atlantic and the Southeast today beneath the upper ridge.
Boundary-layer heating will prove instrumental in convective
development this afternoon, especially along a stalled synoptic
front draped across NC/VA. Forecast soundings for this region
suggest convective temperatures will be breached as early as 17z,
and seasonally high PW values favor some risk for strong wind gusts
within pulse-type updrafts.

..Darrow/Moore.. 08/30/2024

$$

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ACUS01 KWNS 301234
SWODY1
SPC AC 301232

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0732 AM CDT Fri Aug 30 2024

Valid 301300Z - 311200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
EASTERN LOWER MICHIGAN...

...SUMMARY...
Scattered strong to severe thunderstorms are possible across eastern
Lower Michigan this afternoon, with damaging winds the main threat.
Isolated strong to severe thunderstorms may occur into parts of the
Midwest, and also across portions of the Carolinas and Virginia into
northeast Georgia.

...Great Lakes to the Mid Mississippi Valley...
Weak/elevated thunderstorms ongoing this morning from parts of
northern IL into Lower MI should continue to gradually weaken. In
their wake, moderate instability should develop along and ahead of a
cold front that will extend from the Upper Great Lakes region
southwestward to the southern Plains by this afternoon. This front
should make continued slow east-southeastward progress across these
regions through the period as an upper trough moves eastward over
Ontario, the Great Lakes, and Midwest. Stronger mid-level winds
associated with this feature will generally remain confined to
Canada. But, modest enhancement to the west-southwesterly
low/mid-level flow should be present over parts of Lower MI this
afternoon.

Even though low-level convergence along the front should remain
fairly weak, expectations are for at least scattered thunderstorms
to develop along much of its length from eastern Lower MI to the mid
MS Valley and southern Plains. The combination of moderate
instability with modest deep-layer shear should promote some
convective organization, with loosely organized multicells/clusters
likely becoming the dominant thunderstorm mode. Steepened low-level
lapse rates with daytime hearing should encourage occasional strong
to damaging winds, with slightly stronger low/mid-level flow perhaps
supporting a relatively greater threat ahead of the front in eastern
Lower MI. Isolated hail may also occur with the strongest cores.
Convection should weaken with time this evening with the loss of
daytime heating.

...Southern Appalachians to the Southern Mid-Atlantic...
Upper ridging will persist over the Southeast today. Very weak
low/mid-level flow is expected to limit overall thunderstorm
organization. Still, moderate instability should be present this
afternoon as daytime heating occurs along and south of a stalled
front over southern VA and northern NC. Even though deep-layer shear
will remain negligible, pulse-type thunderstorms that develop in
this moderately unstable and high precipitable water environment
could produce isolated strong to damaging downburst winds this
afternoon.

..Gleason/Leitman.. 08/30/2024

$$

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ACUS01 KWNS 301625
SWODY1
SPC AC 301624

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1124 AM CDT Fri Aug 30 2024

Valid 301630Z - 311200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
EASTERN LOWER MICHIGAN...

...SUMMARY...
Scattered strong to severe thunderstorms are possible across eastern
Lower Michigan this afternoon, with damaging winds the main threat.
Isolated strong to severe thunderstorms may occur into parts of the
Midwest, and also across portions of the Carolinas and Virginia into
northeast Georgia.

...Great Lakes to the Mid Mississippi Valley...
Moderate instability is expected to develop ahead of a cold front
that should extend from eastern Lower MI southwest into OK this
afternoon, with MLCAPE on the order of 2000 J/kg. Modestly enhanced
westerly mid-level flow across Lower MI will contribute to 25-35 kts
of deep-layer shear, and this should prove sufficient for organized
multicell storms. Scattered thunderstorm development is expected
this afternoon as weak height falls/ascent overspreads the Slight
Risk area, and where somewhat greater storm coverage is expected.
Substantial boundary layer heating will result in steep low-level
lapse rates, and the strongest storms/clusters will be capable of
damaging gusts and isolated severe hail.

Farther southwest, mid-level flow will be weaker than across the
Great Lakes, but higher MLCAPE and negligible CINH will be present.
Scattered thunderstorms should develop along the front after 18-19z,
tending to cluster with time, and pose a risk for strong/damaging
gusts and perhaps hail.

...Southern Appalachians to the Southern Mid-Atlantic...
Diurnal heating of a very moist air mass (mid/upper 70s surface dew
points and PW generally above 1.75 inches) will result in strong
instability, with pockets of MLCAPE in excess of 3000 J/kg and
effectively no CINH. Despite very weak mid-level flow of 10-15 kts,
scattered thunderstorms developing near a weak front, and over
higher terrain, will pose a risk for a few wet microbursts/strong
wind gusts through this afternoon.

..Bunting/Squitieri.. 08/30/2024

$$

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ACUS01 KWNS 301948
SWODY1
SPC AC 301946

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0246 PM CDT Fri Aug 30 2024

Valid 302000Z - 311200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
EASTERN LOWER MICHIGAN...

...SUMMARY...
Scattered strong to severe thunderstorms are possible across eastern
Lower Michigan this afternoon, with damaging winds the main threat.
Isolated strong to severe thunderstorms may occur into parts of the
Midwest, and also across portions of the Carolinas and Virginia into
northeast Georgia.

...20z Update...
The prior outlook remains valid with only minor modifications. The
thunder area over part of the central Plains and Midwest was trimmed
behind the advancing cold front. The thunder line was also adjusted
eastward over parts of western Lake Michigan.

Across parts of the central Mississippi Valley, several multi-cell
clusters are ongoing. The environment remains broadly favorable for
occasional damaging winds with wet microbursts. The MRGL area was
expanded slightly across parts of MO, IL and IN to better account
for a few of these clusters as they track eastward.

Similarly across parts of the southern Appalachians and western
Carolinas, scattered thunderstorms ongoing over the higher terrain
of northern GA and western SC, will pose a risk for a few wet microbursts/strong wind gusts through this afternoon. The MRGL area
was expanded slightly southwestward to better capture the risk for
occasional damaging wind gusts this afternoon. Otherwise the prior
outlook remains valid, see the previous discussion.

..Marlow/Lyons.. 08/30/2024

.PREV DISCUSSION... /ISSUED 1124 AM CDT Fri Aug 30 2024/

...Great Lakes to the Mid Mississippi Valley...
Moderate instability is expected to develop ahead of a cold front
that should extend from eastern Lower MI southwest into OK this
afternoon, with MLCAPE on the order of 2000 J/kg. Modestly enhanced
westerly mid-level flow across Lower MI will contribute to 25-35 kts
of deep-layer shear, and this should prove sufficient for organized
multicell storms. Scattered thunderstorm development is expected
this afternoon as weak height falls/ascent overspreads the Slight
Risk area, and where somewhat greater storm coverage is expected.
Substantial boundary layer heating will result in steep low-level
lapse rates, and the strongest storms/clusters will be capable of
damaging gusts and isolated severe hail.

Farther southwest, mid-level flow will be weaker than across the
Great Lakes, but higher MLCAPE and negligible CINH will be present.
Scattered thunderstorms should develop along the front after 18-19z,
tending to cluster with time, and pose a risk for strong/damaging
gusts and perhaps hail.

...Southern Appalachians to the Southern Mid-Atlantic...
Diurnal heating of a very moist air mass (mid/upper 70s surface dew
points and PW generally above 1.75 inches) will result in strong
instability, with pockets of MLCAPE in excess of 3000 J/kg and
effectively no CINH. Despite very weak mid-level flow of 10-15 kts,
scattered thunderstorms developing near a weak front, and over
higher terrain, will pose a risk for a few wet microbursts/strong
wind gusts through this afternoon.

$$

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ACUS01 KWNS 310052
SWODY1
SPC AC 310050

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0750 PM CDT Fri Aug 30 2024

Valid 310100Z - 311200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN GREAT LAKES SOUTHWESTWARD INTO THE MID MISSISSIPPI
VALLEY...

...SUMMARY...
Isolated severe storms, with marginally severe wind gusts and hail
will be possible this evening from southeast Lower Michigan
southwestward into the mid Mississippi Valley.

...Southern Great Lakes/Mid Mississippi Valley...
The latest mosaic water vapor imagery shows an upper-level trough
over the western Great Lakes extending southward into the mid
Mississippi Valley. An associated cold front is analyzed from
southeast Lower Michigan southwestward to near St. Louis, Missouri.
Scattered thunderstorms are ongoing along and near the front.
Surface dewpoints near and ahead of the front are in the upper 60s
and lower 70s F, and the RAP has MLCAPE in the 1200 to 2500 J/k/g
range. In addition, regional WSR-88D VWPs near the front have 0-6 km
shear ranging from near 20 knot at St. Louis to around 30 knots at
Detroit. This environment, combined with steep low-level lapse rates
near 7 C/km, should be enough for a marginally severe wind gusts for
a couple more hours this evening. Hail could also occur within the
cores of the stronger multicells.

..Broyles.. 08/31/2024

$$

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ACUS01 KWNS 310602
SWODY1
SPC AC 310601

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0101 AM CDT Sat Aug 31 2024

Valid 311200Z - 011200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL APPALACHIANS AND UPPER OHIO VALLEY...

...SUMMARY...
Severe thunderstorms, associated with severe wind gusts and hail,
will be possible today from parts of the central Appalachians into
the Ohio and Tennessee Valleys. Isolated severe wind gusts will be
possible in parts of the northern Great Lakes.

...Central Appalachians/Ohio and Tennessee Valleys...
An upper-level trough will move through the Great Lakes region, with
the southern end of the trough located in the mid Mississippi
Valley. An associated cold front will advance southeastward through
the mid Mississippi Valley and southern Great Lakes. Ahead of the
front, a moist airmass will be in place with surface dewpoints in
the upper 60s and lower 70s F. Moderate instability is expected to
develop by midday ahead of much of the front. Further to the east, a pre-frontal trough will be located from western New York and western Pennsylvania southwestward into eastern Kentucky. Scattered
thunderstorms will form from near the front eastward to near the
pre-frontal trough. By early to mid afternoon, RAP forecast
soundings have MLCAPE peaking in the 1500 to 2000 J/kg range from
western New York southwestward into West Virginia. Along this
portion of the instability corridor, 0-6 km shear is forecast to be
in the 20 to 30 knot range. This, along with 0-3 km lapse rates near
7.5 C/km will support severe wind gusts with the more organized
bowing line segments. Hail will also be possible.

Further to the southwest into parts of the lower Ohio and Tennessee
Valleys, the models suggest that deep-layer shear will generally be
below 20 knots. Although steep low-level lapse rates could be enough
for a marginal wind-damage threat, the weakness in shear should keep
any threat isolated.

...Northern Great Lakes...
A cyclonic mid-level flow pattern will be in place today across much
of southern Canada and over the Great Lakes. Within this flow, a
shortwave trough and an associated cold front is forecast to move
southeastward toward the northern Great Lakes. Ahead of the front,
surface dewpoints in the 50s F will contribute to weak
destabilization by afternoon. Thunderstorms are expected to form
along and ahead of the front as instability peaks during the mid to
late afternoon. In spite of the weak instability, large-scale ascent
and strong deep-layer shear, associated with the shortwave trough,
could be enough for isolated severe wind gusts.

..Broyles/Moore.. 08/31/2024

$$

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ACUS01 KWNS 311241
SWODY1
SPC AC 311240

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0740 AM CDT Sat Aug 31 2024

Valid 311300Z - 011200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL APPALACHIANS AND UPPER OHIO VALLEY...

...SUMMARY...
Severe thunderstorms capable of producing mainly damaging winds will
be possible today from parts of the central Appalachians into the
Ohio and Tennessee Valleys. Isolated severe wind gusts may also
occur across parts of the northern Great Lakes.

...Mid-Atlantic into the Ohio and Tennessee Valleys...
A mid/upper-level trough will make slow eastward progress today
across Ontario/Quebec and the Great Lakes while amplifying further.
Ahead of this feature, a surface front should continue to lose
definition and weaken through the day as it moves eastward over
parts of the Northeast/Mid-Atlantic, and southeastward over the OH
Valley before eventually stalling. Recent visible satellite imagery
shows cloud cover remains prevalent over much of the Northeast and Mid-Atlantic. This will hinder daytime heating and delay
destabilization, especially east of the Blue Ridge Mountains. Still,
area 12Z soundings and recent surface observations indicate a moist
low-level airmass remains in place ahead of the weak cold front.
Generally less cloud cover with westward and southward extent into
the upper OH Valley and TN Valley should allow for greater
instability to develop this afternoon across these regions.

The stronger mid-level flow associated the upper trough is expected
to remain generally displaced to the north/west of the surface warm
sector. Even so, modestly increasing west-southwesterly winds with
height through mid levels should support around 20-30 kt of
deep-layer shear across parts of the central Appalachians and upper
OH Valley vicinity. This shear will be sufficient for loosely
organized multicell clusters to develop and subsequently spread east-southeastward through this afternoon. Isolated to scattered
damaging winds should be the main threat with this convection,
although some hail may also occur with the strongest cores. Activity
should weaken with eastward extent late this afternoon and evening
across the Mid-Atlantic as it encounters a less unstable airmass.
Weaker deep-layer shear with southward extent into the lower OH
Valley and TN Valley will likely limit overall thunderstorm
organization. But, occasional damaging winds may still occur with
thunderstorms along/south of the front as low-level lapse rates
steepen with diurnal heating.

...Northern Great Lakes...
Strong west-northwesterly mid-level flow will be present today over
the Upper Midwest and northern Great Lakes, in association with a
shortwave trough embedded within a larger upper trough moving east-southeastward across these regions. While low-level moisture
and related instability are both expected to remain limited,
large-scale ascent and strong deep-layer shear may support the
development low-topped convection this afternoon. If these
thunderstorms can form and be sustained, then isolated strong to
severe winds may occur given the forecast strength of the low to
mid-level flow amid steepened low-level lapse rates.

..Gleason/Leitman.. 08/31/2024

$$

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ACUS01 KWNS 311630
SWODY1
SPC AC 311629

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1129 AM CDT Sat Aug 31 2024

Valid 311630Z - 011200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE CENTRAL APPALACHIANS AND UPPER OHIO VALLEY...

...SUMMARY...
Severe thunderstorms capable of producing mainly damaging winds will
be possible today from parts of the central Appalachians into the
Ohio and Tennessee Valleys. Isolated severe wind gusts may also
occur across parts of the northern Great Lakes.

...Mid-Atlantic into the Ohio and Tennessee Valleys...
A mid/upper-level trough will move eastward across Ontario/Quebec
and the Great Lakes today while undergoing some amplification.
Ahead of this feature, a surface front will move eastward over parts
of the Northeast/Mid-Atlantic, and southeastward over the OH Valley
before eventually stalling. A warm front will lift north through the
period across the mid-Atlantic and northeast states. Late morning
visible satellite imagery shows substantial low cloud cover over
much of the Northeast and Mid-Atlantic. This will reduce daytime
heating and delay destabilization, especially east of the Blue Ridge
Mountains. However, with a moist low-level air mass in place, even
modest diurnal heating will result in sufficient destabilization to
support some risk for strong/severe storms.

The stronger mid-level flow associated with the upper trough is
expected to remain generally displaced to the north/west of the
surface warm sector. Even so, modestly increasing west-southwesterly
winds with height through mid levels should support around 20-30 kt
of deep-layer shear across parts of the central Appalachians and
upper OH Valley vicinity. This shear will be sufficient for loosely
organized multicell clusters to develop or intensify and
subsequently spread east-southeastward through this afternoon.
Isolated to scattered damaging winds should be the main threat with
this convection, although some hail may also occur with the
strongest cells. Storms should gradually weaken with eastward extent
by this evening across the Mid-Atlantic while encountering a less
unstable air mass. Weaker deep-layer shear with southward extent
into the lower OH Valley and TN Valley will likely limit overall
thunderstorm organization. However, occasional damaging winds may
still occur with thunderstorms along/south of the front as low-level
lapse rates steepen.

...Northern Great Lakes...
Strong west-northwesterly mid-level flow will exist over
the Upper Midwest and northern Great Lakes in association with a
shortwave trough embedded within a broader cyclonic flow. While
low-level moisture and related instability are both expected to
remain limited, large-scale ascent and strong deep-layer shear may
support the development of low-topped thunderstorms this afternoon.
If these thunderstorms can be sustained, then isolated strong to
severe winds may occur given the forecast strength of the low to
mid-level flow in the presence of steepened low-level lapse rates.

..Bunting/Jewell.. 08/31/2024

$$

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ACUS01 KWNS 311955
SWODY1
SPC AC 311953

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0253 PM CDT Sat Aug 31 2024

Valid 312000Z - 011200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE CENTRAL APPALACHIANS AND UPPER OHIO VALLEY...

...SUMMARY...
Severe thunderstorms capable of producing mainly damaging winds
remain possible this afternoon and evening from parts of the central Appalachians into the Ohio and Tennessee Valleys. Isolated severe
wind gusts may also occur across parts of the northern Great Lakes.

...20Z Update...
Some minor adjustments have been made to the Marginal and Slight
Risks based on observational trends, but no major changes have been
made to the outlook. Scattered damaging winds remain possible
through late afternoon and perhaps into early evening from parts of
WV into western/central PA and western MD/VA. See MCD 2040 regarding
the short-term threat in this area. Also, see the previous
discussion below for more information.

..Dean.. 08/31/2024

.PREV DISCUSSION... /ISSUED 1129 AM CDT Sat Aug 31 2024/

...Mid-Atlantic into the Ohio and Tennessee Valleys...
A mid/upper-level trough will move eastward across Ontario/Quebec
and the Great Lakes today while undergoing some amplification.
Ahead of this feature, a surface front will move eastward over parts
of the Northeast/Mid-Atlantic, and southeastward over the OH Valley
before eventually stalling. A warm front will lift north through the
period across the mid-Atlantic and northeast states. Late morning
visible satellite imagery shows substantial low cloud cover over
much of the Northeast and Mid-Atlantic. This will reduce daytime
heating and delay destabilization, especially east of the Blue Ridge
Mountains. However, with a moist low-level air mass in place, even
modest diurnal heating will result in sufficient destabilization to
support some risk for strong/severe storms.

The stronger mid-level flow associated with the upper trough is
expected to remain generally displaced to the north/west of the
surface warm sector. Even so, modestly increasing west-southwesterly
winds with height through mid levels should support around 20-30 kt
of deep-layer shear across parts of the central Appalachians and
upper OH Valley vicinity. This shear will be sufficient for loosely
organized multicell clusters to develop or intensify and
subsequently spread east-southeastward through this afternoon.
Isolated to scattered damaging winds should be the main threat with
this convection, although some hail may also occur with the
strongest cells. Storms should gradually weaken with eastward extent
by this evening across the Mid-Atlantic while encountering a less
unstable air mass. Weaker deep-layer shear with southward extent
into the lower OH Valley and TN Valley will likely limit overall
thunderstorm organization. However, occasional damaging winds may
still occur with thunderstorms along/south of the front as low-level
lapse rates steepen.

...Northern Great Lakes...
Strong west-northwesterly mid-level flow will exist over
the Upper Midwest and northern Great Lakes in association with a
shortwave trough embedded within a broader cyclonic flow. While
low-level moisture and related instability are both expected to
remain limited, large-scale ascent and strong deep-layer shear may
support the development of low-topped thunderstorms this afternoon.
If these thunderstorms can be sustained, then isolated strong to
severe winds may occur given the forecast strength of the low to
mid-level flow in the presence of steepened low-level lapse rates.

$$

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ACUS01 KWNS 010039
SWODY1
SPC AC 010038

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0738 PM CDT Sat Aug 31 2024

Valid 010100Z - 011200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN GREAT LAKES...

...SUMMARY...
Isolated severe wind gusts will be possible this evening across
parts of the northern Great Lakes.

...Northern Great Lakes...
Water vapor imagery shows a low-amplitude shortwave trough over
southern Ontario extending into northern Minnesota. Ahead of the
shortwave trough, a band of large-scale ascent appears to be moving
through the vicinity of Lake Superior, where a broken line of
thunderstorms is ongoing. Ahead of this line, surface dewpoints are
in the mid 50s F, and the RAP has SBCAPE of 250 to 500 J/kg. RAP
forecast soundings over upper Michigan have strong deep-layer shear
exceeding 60 knots, and steep low to mid-level lapse rates. This may
be enough for an isolated threat of severe wind gusts. This threat
may persist for another hour or two.

..Broyles.. 09/01/2024

$$

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ACUS01 KWNS 010536
SWODY1
SPC AC 010534

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1234 AM CDT Sun Sep 01 2024

Valid 011200Z - 021200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
SOUTHERN APPALACHIANS INTO THE MID-ATLANTIC AND PARTS OF NEW
ENGLAND....

...SUMMARY...
Strong thunderstorms capable of producing damaging wind gusts are
probable this afternoon across the southern Appalachians and
Mid-Atlantic region, as well as across parts of southern New
England.

...Synopsis...
Latest water-vapor imagery depicts a deepening upper trough over the
Great Lakes region with an attendant cold front noted in surface
observations extending from the Great Lakes region into the central
Plains. The northern portion of the cold front will continue to
surge to the east in tandem with the upper trough; to the south, the
front will begin to slow as it becomes increasingly frontolytic over
the TN Valley and Ozark Plateau later today. Thunderstorm
development will mainly be focused along this front as it impinges
on a moist, weakly capped air mass currently in place from the
Mid-MS River Valley into the Mid-Atlantic. More isolated
thunderstorm chances are anticipated across the southern U.S. and
over portions of the Southwest/Great Basin.

...Southern Appalachians/Mid-Atlantic...
Initially isolated thunderstorm development is expected along the
cold front as it approaches the TN Valley/southern Appalachians, but
the weakly capped environment will favor additional development
along convective outflows as well as orographically-initiated
convection within the higher terrain of the southern Appalachians.
As such, convective coverage should increase through mid-afternoon
as storms propagate east into the Mid-Atlantic region. Mid-level
flow on the southern periphery of the upper trough will be strong
enough to support around 20 knots of effective bulk shear, which
should support loosely organized convective clusters/multi-cells
with an attendant risk for damaging wind gusts. Recent CAM guidance
suggests central NC/VA may see the best potential for such clusters,
and consequently could have a relatively higher potential for
damaging winds.

Further to the northeast into parts of southern New England,
thunderstorm coverage is expected to be much more isolated and tied
primarily to a deepening surface trough during the mid/late
afternoon hours. While buoyancy will remain somewhat meager due to
poor mid-level lapse rates, stronger mid-level flow in closer
proximity to the upper trough may support an organized storm or two.


...Northwest New York...
Consideration for a small Marginal risk area was made across far
northwest NY. Forcing along the cold front will be much stronger
along the international border with several CAM solutions hinting
that shallow convection may accompany the front with an attendant
damaging wind risk (as was observed Saturday evening across the
upper Great Lakes region). However, warmer mid-level temperatures
further over the Northeast should limit overall buoyancy values and
casts uncertainty onto convective depth and intensity. Additionally,
most CAM solutions hint that this potential will remain fairly
confined to along the NY international border. Due to these concerns
risk probabilities were withheld, but trends will continue to be
monitored.

..Moore.. 09/01/2024

$$

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ACUS01 KWNS 011250
SWODY1
SPC AC 011248

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0748 AM CDT Sun Sep 01 2024

Valid 011300Z - 021200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
THE SOUTHERN APPALACHIANS INTO THE MID-ATLANTIC AND SOUTHERN NEW
ENGLAND...

...SUMMARY...
Strong thunderstorms capable of producing isolated damaging winds
may occur this afternoon across parts of the southern Appalachians
into the Mid-Atlantic and southern New England.

...Southern Appalachians into the Mid-Atlantic and Southern New
England...
Thunderstorms should gradually increase in coverage this afternoon
along/south of a weak front that extends from the Mid-South/lower OH
Valley into the Mid-Atlantic. Morning visible satellite imagery
shows plentiful cloud cover near this boundary, and downstream
across parts of NC and the Mid-Atlantic into southern New England.
Still, filtered daytime heating of a moist low-level airmass should
allow at least weak instability to develop by early to mid afternoon
along and south/east of the front, even though mid-level lapse rates
will remain poor.

The glancing influence/ascent of an upper trough over eastern
Canada, along with weak orographic lift, will likely encourage
convection development through the afternoon and early evening.
Mid-level flow and related deep-layer shear are forecast to remain
fairly modest, especially with southward extent across the
Mid-Atlantic into the Carolinas and southern Appalachians. Still,
enough flow and related shear may be present to support modest
thunderstorm organization. Multiple loosely organized multicell
clusters may eventually develop and consolidate by late afternoon
and early evening, while posing some threat for isolated strong to
damaging winds as they move generally eastward. The greatest
concentration of thunderstorms should exist across parts of southern
VA into NC and upstate SC where greater instability is forecast this
afternoon. But, confidence in a more organized wind threat remains
too low to include greater severe wind probabilities.

...Western/Northern New York into Northern New England...
As the primary upper trough and related surface cold front continue
eastward across Ontario/Quebec today, daytime heating of a modestly
moist low-level airmass will occur over parts of western/northern
NY. Although poor mid-level lapse rates will likely hinder the
development of any more than weak instability across this area
(MLCAPE generally 500 J/kg of less), low/mid-level winds and related
shear in the cloud-bearing layer is expected to strengthen through
this afternoon with the approach of the upper trough. Some high-resolution/convection-allowing model guidance shows a
low-topped line of thunderstorms developing this afternoon along or
just ahead of the cold front. As low-level lapse rates steepen with
daytime heating, some of this convection could produce isolated
strong to severe wind gusts given the strengthening low/mid-level
flow expected. The area impacted should remain fairly small across western/northern NY (generally downstream of Lake Ontario) due to
more even more limited instability farther east across central NY
into northern New England.

..Gleason/Leitman.. 09/01/2024

$$

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ACUS01 KWNS 011626
SWODY1
SPC AC 011625

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1125 AM CDT Sun Sep 01 2024

Valid 011630Z - 021200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
THE SOUTHERN APPALACHIANS INTO THE MID-ATLANTIC AND SOUTHERN NEW
ENGLAND...

...SUMMARY...
Strong to severe thunderstorms capable of producing isolated
damaging winds may occur this afternoon across parts of the southern Appalachians into the Mid-Atlantic and southern New England.

...Southern Appalachians into the Mid-Atlantic and Southern New
England...
Thunderstorms should gradually increase in coverage this afternoon
along/south of a diffuse front that extends from the Mid-South/lower
OH Valley into the Mid-Atlantic. Late morning visible satellite
imagery shows substantial cloud cover in the vicinity of the
boundary. Nevertheless, daytime heating of a moist low-level air
mass should allow at least weak/pockets of moderate instability to
develop by early to mid afternoon along and south/east of the front.

Modest ascent with an upper trough over eastern Canada and adjacent
Great Lakes/Northeast U.S., in combination with orographic ascent,
will likely contribute to thunderstorm development through the
afternoon and early evening. Mid-level flow and related deep-layer
shear will remain fairly modest, especially with southward extent
across the Mid-Atlantic into the Carolinas and southern
Appalachians. Mid-level flow should still prove sufficient to
support modest thunderstorm organization. Multiple loosely
organized multicell clusters may eventually develop and consolidate
by late afternoon and early evening, posing some threat for isolated
strong to damaging winds while moving generally eastward. The
greatest concentration of thunderstorms should exist across parts of
southern VA into NC and upstate SC where greater instability (MLCAPE
on the order of 2000-2500 J/kg) is forecast this afternoon.

...Western/Northern New York into Northern New England...
The upper-level trough and associated surface cold front will move
east today across Ontario/Quebec provinces and Northeast U.S., with
weak surface-based instability possibly developing in advance of the
front. This may result in a narrow, low-topped line of convection
(possibly with little lightning) moving east and accompanied by some
risk for strong/locally damaging gusts.

..Bunting/Bentley.. 09/01/2024

$$

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ACUS01 KWNS 011956
SWODY1
SPC AC 011955

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0255 PM CDT Sun Sep 01 2024

Valid 012000Z - 021200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF
UPSTATE NEW YORK AND SOUTHERN NEW ENGLAND INTO THE CAROLINAS AND
SOUTHERN APPALACHIANS...

...SUMMARY...
Strong to severe thunderstorms capable of producing isolated
damaging winds may still occur this afternoon across parts of the
southern Appalachians into the Mid-Atlantic and southern New
England.

...20Z Update...
The previous forecast remains on track, with only slight changes
made to the thunder line to reflect the latest guidance consensus
and observations.

..Squitieri.. 09/01/2024

.PREV DISCUSSION... /ISSUED 1125 AM CDT Sun Sep 01 2024/

...Southern Appalachians into the Mid-Atlantic and Southern New
England...
Thunderstorms should gradually increase in coverage this afternoon
along/south of a diffuse front that extends from the Mid-South/lower
OH Valley into the Mid-Atlantic. Late morning visible satellite
imagery shows substantial cloud cover in the vicinity of the
boundary. Nevertheless, daytime heating of a moist low-level air
mass should allow at least weak/pockets of moderate instability to
develop by early to mid afternoon along and south/east of the front.

Modest ascent with an upper trough over eastern Canada and adjacent
Great Lakes/Northeast U.S., in combination with orographic ascent,
will likely contribute to thunderstorm development through the
afternoon and early evening. Mid-level flow and related deep-layer
shear will remain fairly modest, especially with southward extent
across the Mid-Atlantic into the Carolinas and southern
Appalachians. Mid-level flow should still prove sufficient to
support modest thunderstorm organization. Multiple loosely
organized multicell clusters may eventually develop and consolidate
by late afternoon and early evening, posing some threat for isolated
strong to damaging winds while moving generally eastward. The
greatest concentration of thunderstorms should exist across parts of
southern VA into NC and upstate SC where greater instability (MLCAPE
on the order of 2000-2500 J/kg) is forecast this afternoon.

...Western/Northern New York into Northern New England...
The upper-level trough and associated surface cold front will move
east today across Ontario/Quebec provinces and Northeast U.S., with
weak surface-based instability possibly developing in advance of the
front. This may result in a narrow, low-topped line of convection
(possibly with little lightning) moving east and accompanied by some
risk for strong/locally damaging gusts.

$$

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ACUS01 KWNS 020043
SWODY1
SPC AC 020042

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0742 PM CDT Sun Sep 01 2024

Valid 020100Z - 021200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated to scattered thunderstorms will continue into the late
evening and overnight hours from the Mid-Atlantic region into the
southern CONUS, Four Corners region, and Pacific Northwest.

...Summary...
Isolated to scattered thunderstorms are expected to persist into the
early morning hours across parts of the Mid-Atlantic, but the
overall severe threat appears sufficiently low to remove risk
probabilities.

...Mid-Atlantic...
Thunderstorms across the Mid-Atlantic region have shown signs of
steady weakening over the past hour based on regional reflectivity
imagery, MRMS echo-top heights, and cloud-top temperatures. 00 UTC
soundings along the East Coast, and downstream from ongoing
multicell clusters, sampled around 500-1000 J/kg MLCAPE with around
20 knots of mid-level flow. A sporadic strong updraft or two will
remain possible this evening along the outflow boundaries of ongoing
convection given these environmental conditions. However, the onset
of nocturnal cooling will continue to modulate mixed-layer buoyancy
(with an attendance increase in inhibition), which should maintain
the overall weakening trend. Latest CAM solutions support this
scenario with increasingly sparse thunderstorm coverage heading into
the early morning hours. Consequently, the overall severe potential
appears sufficiently low to warrant removing risk probabilities.

..Moore.. 09/02/2024

$$

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ACUS01 KWNS 020542
SWODY1
SPC AC 020541

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1241 AM CDT Mon Sep 02 2024

Valid 021200Z - 031200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL
TO WESTERN IDAHO AND ADJACENT PORTIONS OF NEVADA AND OREGON...

...SUMMARY...
Isolated to scattered thunderstorms across the northern Great Basin
and parts of the Pacific Northwest may be capable of strong to
severe wind gusts this afternoon and evening.

...Synopsis...
Recent water-vapor imagery depicts a dominant upper ridge centered
over the central CONUS. Flanking the ridge is a departing upper
trough across the lower Great Lakes/Northeast and a more compact
shortwave trough off the northern California coast. This upper-air
regime will largely remain intact for the next 24 hours as the
Northeast upper wave continues to move into the western Atlantic and
the CA shortwave migrates towards the northern Rockies. At the
surface, a slowing cold front draped from the Northeast into the
southern Plains will continue to meander south through the day as a
surface high builds over the Midwest. Isolated to scattered
thunderstorms will be possible along this front and in the vicinity
of a weak mid-level disturbance over western TX; however, weak flow
aloft will hinder the potential for organized convection. Across the
West, thunderstorms, including a few strong to severe storms, are
expected ahead of the upper trough as it moves onshore over the next
24 hours.

...Nevada into eastern Oregon and Idaho...
A modest plume of monsoonal moisture has been tracked from southern
AZ into northern NV/eastern OR over the past few days, and has
resulted in multiple rounds of thunderstorms across the Great Basin
despite very limited low-level moisture and only modestly cool
mid-level temperatures. These conditions were well-sampled by the 00
UTC MFR sounding, which depicts around 250 J/kg MLCAPE atop a very
deep, dry boundary layer. This profile will be typical this
afternoon across the region as ascent associated with the
approaching wave overspreads the northern Great Basin/Pacific
Northwest. Despite minimal buoyancy, LCL heights between 3-4 km will
foster ample evaporative cooling of convective downdrafts that will
support strong downburst winds. Increasing flow throughout the
column will improve wind shear within the CAPE-bearing layer,
promoting better storm longevity and organization (and hence a
higher potential for producing strong/severe wind gusts) compared to
previous days. Recent CAM solutions also hint at this potential with
several HREF members showing isolated swaths of severe winds across
northern NV into central and western ID and eastern OR.

..Moore/Kerr.. 09/02/2024

$$

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ACUS01 KWNS 021240
SWODY1
SPC AC 021238

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0738 AM CDT Mon Sep 02 2024

Valid 021300Z - 031200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE INTERIOR PACIFIC NORTHWEST INTO THE NORTHERN GREAT
BASIN/ROCKIES...

...SUMMARY...
Isolated to scattered thunderstorms across the northern Great Basin
and parts of the interior Pacific Northwest may be capable of
occasional strong to severe wind gusts this afternoon and evening.

...Interior Pacific Northwest into the Northern Great
Basin/Rockies...
A closed upper low approaching the northern CA and OR Coast will
continue eastward today across the Pacific Northwest and northern
Great Basin. Associated 35-50 kt mid-level south-southwesterlies
will overspread these regions through the afternoon and evening.
Large-scale ascent attendant to the upper low has already encouraged
weak, elevated convection this morning across pats of eastern OR and
vicinity. Current expectations are for additional showers and
thunderstorms to develop later this afternoon as daytime heating
occurs, mainly across parts of central/eastern OR into ID and
northern NV/northwest UT. This convection will likely be rather
high-based (LCLs around 3-4 km AGL), as latest surface observations
and area 12Z soundings show very limited low-level moisture, and
total PWAT values generally 0.5-0.7 inches. Even with rather weak
buoyancy forecast across much of this area, a deeply mixed boundary
layer should encourage efficient evaporative cooling of convective
downdrafts. An isolated risk for strong/gusty winds approaching and occasionally exceeding severe levels remains apparent with this
high-based convection as it spreads generally north-northeastward
through the afternoon/evening before eventually weakening.

..Gleason/Leitman.. 09/02/2024

$$

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ACUS01 KWNS 021619
SWODY1
SPC AC 021618

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1118 AM CDT Mon Sep 02 2024

Valid 021630Z - 031200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE INTERIOR PACIFIC NORTHWEST INTO THE NORTHERN GREAT
BASIN/ROCKIES...

...SUMMARY...
Isolated to scattered thunderstorms across the northern Great Basin
and parts of the interior Pacific Northwest may be capable of
occasional strong to severe wind gusts this afternoon and evening.

...Interior Pacific Northwest into the Northern Great
Basin/Rockies...
Water-vapor imagery this morning shows a closed low near the
northern CA/southern OR coast. This upper feature will move east
through OR and be situated along the OR/ID border by daybreak
Tuesday. A belt of stronger flow (30-50 kt 500-mb winds) will move
through the base of the larger-scale mid-level trough and overspread
northern NV into southwestern ID and eastern OR this afternoon into
the early evening. Large-scale ascent associated with the upper
disturbance and the development of weak buoyancy (mainly via
heating), will facilitate the development of isolated to scattered
high-based thunderstorms beginning later this afternoon and
persisting into the evening. Forecast soundings show large surface temperature-dewpoint spreads (50 degrees F) with 9+ degrees C lapse
rates into the mid levels and a dry sub-cloud layer. Evaporative
cooling of the more intense downdrafts will probably yield a risk
for isolated 60-70 mph gusts before weakening later this evening.

..Smith/Squitieri.. 09/02/2024

$$

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ACUS01 KWNS 021952
SWODY1
SPC AC 021950

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0250 PM CDT Mon Sep 02 2024

Valid 022000Z - 031200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE NORTHERN GREAT BASIN AND THE NORTHWEST...

...SUMMARY...
Isolated to scattered thunderstorms across the northern Great Basin
and parts of the interior Pacific Northwest may be capable of
occasional strong to severe wind gusts this afternoon and evening.

...20Z Update...
Minor adjustments were made to the general thunderstorm area to
account for current observed trends. The remainder of the forecast
is unchanged. See the previous discussion for additional details.

..Wendt.. 09/02/2024

.PREV DISCUSSION... /ISSUED 1118 AM CDT Mon Sep 02 2024/

...Interior Pacific Northwest into the Northern Great
Basin/Rockies...
Water-vapor imagery this morning shows a closed low near the
northern CA/southern OR coast. This upper feature will move east
through OR and be situated along the OR/ID border by daybreak
Tuesday. A belt of stronger flow (30-50 kt 500-mb winds) will move
through the base of the larger-scale mid-level trough and overspread
northern NV into southwestern ID and eastern OR this afternoon into
the early evening. Large-scale ascent associated with the upper
disturbance and the development of weak buoyancy (mainly via
heating), will facilitate the development of isolated to scattered
high-based thunderstorms beginning later this afternoon and
persisting into the evening. Forecast soundings show large surface temperature-dewpoint spreads (50 degrees F) with 9+ degrees C lapse
rates into the mid levels and a dry sub-cloud layer. Evaporative
cooling of the more intense downdrafts will probably yield a risk
for isolated 60-70 mph gusts before weakening later this evening.

$$

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ACUS01 KWNS 030043
SWODY1
SPC AC 030042

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0742 PM CDT Mon Sep 02 2024

Valid 030100Z - 031200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS EVENING
ACROSS PARTS OF NORTHEASTERN OREGON...SOUTHEASTERN
WASHINGTON...CENTRAL IDAHO AND ADJACENT SOUTHWESTERN MONTANA...

...SUMMARY...
Widely scattered strong to severe wind gusts remain possible near
lingering thunderstorm activity across parts of the northern
Intermountain Region through this evening.

...01Z Update...
Lower/mid-tropospheric subsidence and drying are probably tending to
suppress ongoing scattered thunderstorm development across the Great
Basin into adjacent northern Intermountain Region. However, widely
scattered stronger thunderstorm development remains possible into
this evening, within favorable large-scale forcing for ascent in the
exit region of a vigorous upper jet streak (including 70+ kt around
300 mb) nosing north-northeastward through eastern Oregon, and in
the downstream lower/mid-level warm advection regime overspreading
central Idaho. Even within this regime, higher precipitable water
on the order of .7-.8 inches appears to be supporting only weak CAPE
(e.g. little more than 100 J/kg of mixed-layer CAPE in the 03/00Z
sounding from Boise, ID), and this is limiting the strength of the
updrafts and associated precipitation, which in turn is limiting the
strength of downdraft potential despite being rooted above a warm
and deeply mixed boundary layer. The potential for stronger gusts,
aided by downward mixing of higher momentum from aloft, seems likely
to remain generally focused across the higher elevations of north
central and northeastern Oregon into the mountains of central Idaho,
before convection weakens later this evening.

..Kerr.. 09/03/2024

$$

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ACUS01 KWNS 030535
SWODY1
SPC AC 030533

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1233 AM CDT Tue Sep 03 2024

Valid 031200Z - 041200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
INTO THIS EVENING ACROSS PARTS OF CENTRAL IDAHO...MUCH OF SOUTHERN MONTANA...WYOMING...MUCH OF NORTHERN UTAH AND ADJACENT NORTHWESTERN COLORADO...INTO PARTS OF THE WESTERN DAKOTAS...

...SUMMARY...
Thunderstorms developing across the northern Rockies and adjacent
portions of the Great Basin by this afternoon may produce scattered
strong to locally severe wind gusts, before spreading eastward
toward the northern Great Plains into this evening.

...Synopsis...
Downstream of split mid/upper flow across the eastern Pacific,
Alaska and Canadian Yukon vicinity, the stronger westerlies remain
confined to the higher latitudes, with weaker zonal flow prevailing
across the northern tier of the U.S., on the northern periphery of weak/suppressed subtropical ridging. Seasonably moist
boundary-layer air has generally become confined to the southern
tier of the U.S., to the south of notable surface ridging. Little
change appears likely through this period, though the center of the
ridge may shift from the lower Great Lakes/upper Ohio Valley into
the northern Mid Atlantic.

It does appear that the westerlies may undergo some amplification
across the northeastern Pacific into Canada later today through
tonight, including building mid-level ridging offshore of the
Pacific Northwest and British Columbia coast and digging mid-level
troughing to the lee of the Canadian Rockies. As this occurs, a
remnant mid-level trough over the interior northwestern U.S. is
forecast to slowly shift into and across the northern Rockies.

...Northern Intermountain Region and Rockies...
Models indicate that the mid-level trough will weaken while shifting
eastward today, but it still appears that mid-level forcing for
ascent and cooling will remain sufficient to support continuing
convective development, including considerable thunderstorm activity
this afternoon and evening across the higher terrain. Near the
mid-level cold core, destabilization, including mixed-layer CAPE on
the order of 500-1000 J/kg, might support a few thunderstorms
capable of producing marginally severe hail across the mountains of southwestern Montana. Otherwise, more modest CAPE, based above a
warm and deeply mixed boundary layer, may still become supportive of
locally strong to severe downburst winds across the higher terrain
of western Wyoming and northern Utah, into the Great Salt Lake
Desert.

Eastward into the northern high plains, severe weather potential,
and the extent to which destabilization is able to maintain
thunderstorm development, remains more uncertain. However, some
model output, perhaps most notably the past few runs of the NAM, has
been suggestive that convective development near/north of the
Absaroka Range and Big Horn Basin vicinity may generate sufficient consolidating outflow to support a substantive east-southeastward
propagating surface cold pool to the lee of the higher terrain.
Although 03/00Z NAM forecast soundings, for example, are not
particularly indicative that vigorous thunderstorm development will
be maintained, they suggest that 35-50 kt winds may accompany a
surging gust front, in this run across southeastern Montana and
adjacent northeastern Wyoming by late evening and into western South
Dakota overnight.

..Kerr/Moore.. 09/03/2024

$$

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ACUS01 KWNS 031235
SWODY1
SPC AC 031234

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0734 AM CDT Tue Sep 03 2024

Valid 031300Z - 041200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN ROCKIES/GREAT BASIN AND ADJACENT HIGH PLAINS...

...SUMMARY...
Thunderstorms developing across the northern Rockies and adjacent
portions of the Great Basin this afternoon may produce occasional
strong to severe wind gusts, before spreading eastward toward the
northern High Plains this evening.

...Northern Great Basin/Rockies into the Adjacent High Plains...
An upper trough/low over the Pacific Northwest this morning will
continue moving eastward today across the northern Rockies. This
feature is forecast to gradually weaken through the period, but
enhanced mid-level west-southwesterly flow will persist across parts
of the northern Great Basin into the northern Rockies and adjacent
High Plains. As large-scale ascent associated with the upper trough
overspreads the northern Rockies, thunderstorms should develop over
the higher terrain through early afternoon in tandem with daytime
heating.

Latest surface observations show somewhat greater low-level moisture
across this region, with surface dewpoints generally in the mid 40s
to low 50s across central ID into southwest MT. Although instability
is forecast to remain fairly modest this afternoon, deep-layer shear
around 25-35 kt should be sufficient to support organized
convection, including the potential for a couple of marginal
supercells initially with associated hail/wind threat. With
steepened low/mid-level lapse rates present, this activity should
continue to pose some threat for isolated strong to severe wind
gusts as it congeals and spreads east-northeastward across parts of
the northern High Plains through this evening.

Somewhat more limited low-level moisture should be present this
afternoon farther south into WY and northern UT. Even so, diurnal
heating will aid in a deeply mixed boundary layer by this afternoon,
and steep mid-level lapse rates are also expected to remain over
this region. The net result will be high-based thunderstorms capable
of producing isolated strong to severe winds initially developing
across northern UT into far eastern ID, and subsequently moving east-northeastward over WY through the evening. Confidence in a more concentrated corridor of severe winds remains generally low at this
time given the weak instability and modest deep-layer shear
forecast, especially with southward extent into the northern Great
Basin and WY.

..Gleason/Leitman.. 09/03/2024

$$

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ACUS01 KWNS 031631
SWODY1
SPC AC 031630

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1130 AM CDT Tue Sep 03 2024

Valid 031630Z - 041200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN ROCKIES/GREAT BASIN AND ADJACENT HIGH PLAINS...

...SUMMARY...
Scattered thunderstorms developing across the northern Rockies and
adjacent portions of the Great Basin this afternoon may yield an
isolated severe risk, before spreading eastward toward the northern
High Plains this evening.

...Northern Great Basin/Rockies into the Adjacent High Plains... Visible-satellite imagery this morning shows a smoke-encased mid to
upper-level low/vorticity maximum over central ID. This upper
feature will move to near southwest MT/eastern ID late tonight. The
satellite data late this morning shows agitated cumulus developing
immediately ahead of the vorticity max near the ID/MT border, and as large-scale ascent spreads east, additional thunderstorms (widely
scattered to scattered coverage) should develop over the higher
terrain through early afternoon in tandem with daytime heating.

Forecast soundings across southwest MT into northwest WY show
500-1000 J/kg MLCAPE with some elongation of the hodograph. A few
of the stronger storms will probably acquire transient supercell characteristics and have an associated hail/wind threat. Some
clustering may eventually evolve by early evening as storms move
into south-central MT and adjacent parts of northern WY.

Somewhat more limited low-level moisture should be present this
afternoon farther south into WY and northern UT. Even so, diurnal
heating will aid in a deeply mixed boundary layer by this afternoon,
and steep mid-level lapse rates are also expected to remain over
this region. The net result will be high-based thunderstorms capable
of producing isolated severe gusts initially developing across
northern UT into far eastern ID, and subsequently moving
east-northeastward over WY through the evening.

..Smith/Flournoy/Squitieri.. 09/03/2024

$$

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ACUS01 KWNS 031946
SWODY1
SPC AC 031944

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0244 PM CDT Tue Sep 03 2024

Valid 032000Z - 041200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN ROCKIES/GREAT BASIN AND ADJACENT HIGH PLAINS...

...SUMMARY...
Scattered thunderstorms developing across the northern Rockies and
adjacent portions of the Great Basin this afternoon will pose an
isolated severe risk, before spreading eastward toward the northern
High Plains this evening.

...20Z Update...
The previous forecast remains on track, and no changes were made
with this update. Widely scattered thunderstorms are evolving across
the northern Rockies and adjacent Great Basin this afternoon. These
storms are generally focused in a band of midlevel ascent preceding
a compact midlevel low tracking eastward across central ID. This
activity will continue spreading east-northeastward through the
afternoon, with initial semi-discrete clusters/transient supercells
posing a risk of sporadic, marginally severe hail and locally severe
gusts. See MCDs 2044/2045 for details on the near-term severe risk.

Later this afternoon, a more-focused corridor of severe-wind
potential is possible from portions of northwest WY into southwest/south-central MT, especially with any upscale-grown
clusters amid steep deep-layer lapse rates. A 15-percent wind-driven
Slight Risk was considered here, though confidence in the
development of an organized/consolidated cold pool remains too low
for an upgrade.

..Weinman.. 09/03/2024

.PREV DISCUSSION... /ISSUED 1130 AM CDT Tue Sep 03 2024/

...Northern Great Basin/Rockies into the Adjacent High Plains... Visible-satellite imagery this morning shows a smoke-encased mid to
upper-level low/vorticity maximum over central ID. This upper
feature will move to near southwest MT/eastern ID late tonight. The
satellite data late this morning shows agitated cumulus developing
immediately ahead of the vorticity max near the ID/MT border, and as large-scale ascent spreads east, additional thunderstorms (widely
scattered to scattered coverage) should develop over the higher
terrain through early afternoon in tandem with daytime heating.

Forecast soundings across southwest MT into northwest WY show
500-1000 J/kg MLCAPE with some elongation of the hodograph. A few
of the stronger storms will probably acquire transient supercell characteristics and have an associated hail/wind threat. Some
clustering may eventually evolve by early evening as storms move
into south-central MT and adjacent parts of northern WY.

Somewhat more limited low-level moisture should be present this
afternoon farther south into WY and northern UT. Even so, diurnal
heating will aid in a deeply mixed boundary layer by this afternoon,
and steep mid-level lapse rates are also expected to remain over
this region. The net result will be high-based thunderstorms capable
of producing isolated severe gusts initially developing across
northern UT into far eastern ID, and subsequently moving
east-northeastward over WY through the evening.

$$

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ACUS01 KWNS 040043
SWODY1
SPC AC 040041

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0741 PM CDT Tue Sep 03 2024

Valid 040100Z - 041200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL AND NORTHERN ROCKIES INTO THE NORTHERN HIGH PLAINS...

...SUMMARY...
Isolated severe storms, associated with marginally severe wind
gusts, will be possible this evening across parts of the central and
northern Rockies into the northern High Plains.

...Central and Northern Rockies/Northern High Plains...
A positively-tilted upper-level trough is evident on water vapor
imagery over the northern Rockies, with southwest mid-level flow
from the Intermountain West into the northern High Plains. A weakly
unstable airmass is located ahead of the trough from Wyoming
northward into southern and central Montana, with scattered
thunderstorms ongoing near the instability axis. RAP forecast
soundings this evening from west of Billings, Montana southward to
near Jackson, Wyoming have MLCAPE near 500 J/kg, 0-6 km shear around
40 knots and 700-500 mb lapse near 8 C/km. This environment should
continue to support an isolated severe threat. Although instability
is the limiting factor, the threat could continue for a few more
hours this evening before surface temperatures cool significantly.
The primary threat will be for marginally severe wind gusts. Hail
will be possible from south-central Montana into northwest Wyoming,
where large-scale ascent appears to be maximized ahead of the
approaching upper-level trough. The severe threat could impact areas
further to the east in the northern High Plains later this evening.

..Broyles.. 09/04/2024

$$

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ACUS01 KWNS 040536
SWODY1
SPC AC 040534

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1234 AM CDT Wed Sep 04 2024

Valid 041200Z - 051200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTH-CENTRAL ROCKIES...CENTRAL AND NORTHERN PLAINS...AND UPPER
MISSISSIPPI VALLEY...

...SUMMARY...
Isolated severe storms, capable of severe wind gusts and hail, will
be possible this afternoon and evening across parts of the central
and northern Rockies, and from the central and northern Plains into
the upper Mississippi Valley.

...North-central Rockies/Central and Northern Plains/Upper
Mississippi Valley...
A positively-tilted upper-level trough will move across the northern
High Plains and north-central Rockies today. An associated cold
front will move across the northern Plains and central High Plains.
As surface temperatures warm, isolated to scattered thunderstorms
are expected to develop in the higher terrain of the north-central
Rockies in the post-frontal airmass. Additional storms are expected
to form along and near the front across parts of the northern
Plains. The storms will move east and southward across the region,
affecting the central Plains and upper Mississippi during the mid to
late evening. A chance for storms could persist into the overnight.

Model forecasts suggest that the strongest instability will be
located over the eastern Dakotas today, where the development of
moderate instability will be possible. Weak instability is forecast
to develop ahead of the front from the central Rockies and central
High Plains northward into the post-frontal airmass as far north as
eastern Montana. Due to the approaching upper-level trough, moderate
deep-layer shear and steep mid-level lapse rates are forecast across
much of the north-central U.S. The environment should be sufficient
for an isolated severe threat during the afternoon and evening,
especially in areas that sufficiently destabilize. Severe wind gusts
and hail will be possible with the stronger multicells. An isolated
supercell threat could develop in areas where parameters become most
favorable, but location uncertainty is considerable.

..Broyles/Moore.. 09/04/2024

$$

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ACUS01 KWNS 041218
SWODY1
SPC AC 041216

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0716 AM CDT Wed Sep 04 2024

Valid 041300Z - 051200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL ROCKIES INTO THE NORTHERN/CENTRAL PLAINS AND UPPER
MISSISSIPPI VALLEY...

...SUMMARY...
Isolated strong to severe thunderstorms capable of gusty winds and
hail may occur this afternoon and evening across parts of the
central Rockies into the northern/central Plains and upper
Mississippi Valley.

...Central Rockies into the Northern/Central Plains and Upper
Mississippi Valley...
A weak shortwave trough over the northern Rockies and adjacent Great
Basin this morning will become absorbed later today into an
amplifying upper trough over the Canadian Prairie provinces and
northern Plains. At the surface, a cold front related to the upper
trough will continue southward over the northern Plains, and
southeastward across the Upper MS Valley through the period. Modest
low-level moisture is forecast to be in place ahead of this boundary
across the northern Plains and upper MS Valley, with more limited
moisture expected farther west across the central Rockies and
adjacent High Plains. Relatively cool mid-level temperatures
associated with the weak shortwave trough and the presence of steep
mid-level lapse rates should aid in the development of weak
instability across parts of WY, northern CO, and vicinity this
afternoon. Sufficient deep-layer shear (generally 25-35 kt) should
support some updraft organization with convection that initially
forms over the higher terrain before subsequently spreading
eastward. Isolated instances of marginally severe hail and
strong/gusty winds may occur with the more cellular development.
But, some increase in strong to severe wind potential may be
realized as thunderstorms move into an area of steeper low-level
lapse rates across the central High Plains by late this afternoon
and early evening, especially if any small clusters can form.

The severe potential along much of the length of the front in the
northern Plains and upper MS Valley appears rather conditional.
While large-scale ascent associated with the approaching upper
trough should gradually overspread the warm sector by late
afternoon/early evening, most guidance continues to suggest that a
cap and substantial MLCIN will hinder robust convection from
developing through much of the day. Even so, sufficient instability
and shear should be in place along/ahead of the front to support an
isolated hail/wind threat if thunderstorms can form and be sustained
through the evening and early overnight period. The post-frontal
regime across much of MT into ND and western SD appears unlikely to
support severe convection. Accordingly, the Marginal Risk has been
trimmed southward to account for recent guidance and observational
trends.

..Gleason/Leitman.. 09/04/2024

$$

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ACUS01 KWNS 041626
SWODY1
SPC AC 041624

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1124 AM CDT Wed Sep 04 2024

Valid 041630Z - 051200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL ROCKIES INTO THE NORTHERN/CENTRAL PLAINS AND UPPER
MISSISSIPPI VALLEY...

...SUMMARY...
Isolated strong to severe thunderstorms capable of gusty winds and
hail may occur this afternoon and evening across parts of the
central Rockies into the northern/central Plains and upper
Mississippi Valley.

...Central Rockies into the central High Plains...
Recent satellite imagery reveals a broad shortwave trough currently
moving through southern ID and northern NV/UT. This shortwave trough
and accompanying cold mid-level temperatures are forecast to
continue eastward throughout the day, progressing across WY and
northern CO. Modest buoyancy, fostered mainly by cooling mid-level temperatures, is anticipated across WY and adjacent parts of
northern CO as the shortwave trough progresses through. Thunderstorm development is expected as the large-scale ascent attendant to the
shortwave trough interacts with this buoyancy during the afternoon.
Moderate mid-level westerlies will accompany this shortwave trough
as well, with the resulting increase in vertical shear supporting
the potential for a few more organized/persistent storms. Initially
more cellular development across the higher terrain could pose a
risk for isolated hail, particularly across south-central WY and
north-central CO where the best overlap between the stronger shear
and cold mid-level temperatures is expected. Damaging wind gusts are
possible as well, particularly as the storms reach the lower
elevations of central High Plains where a deeply mixed boundary
layer will be in place.

...Central Plains into the Upper MS Valley...
Recent surface analysis places a low over southeast ND, with weak
troughing extending southwestward from this low in east-central CO.
The primary cold front is west of this surface trough, extending
from the low over southeast ND into more of northwest SD and
adjacent northeast WY. The surface low is forecast to progress east-southeastward throughout the day, reaching south-central MN by
late tonight. The attendant cold front is expected to push southward
during the same period, progressing through much of NE by early
Thursday morning.

Warm mid-level temperatures should preclude thunderstorm development
along the surface trough during the afternoon and evening. A few
isolated storms are possible during the evening behind the front as
the shortwave trough ejects out into the central Plains. Additional thunderstorm development is expected overnight/early Thursday
morning across the Upper MS Valley, with some isolated hail possible
within the strongest storms.

..Mosier/Flournoy.. 09/04/2024

$$

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ACUS01 KWNS 042000
SWODY1
SPC AC 041959

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Wed Sep 04 2024

Valid 042000Z - 051200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL ROCKIES INTO THE NORTHERN/CENTRAL PLAINS AND UPPER
MISSISSIPPI VALLEY...

...SUMMARY...
Isolated strong to severe thunderstorms capable of gusty winds and
hail may occur this afternoon and evening across parts of the
central Rockies into the northern/central Plains and upper
Mississippi Valley.

...20Z Update...
The forecast remains on track, and no appreciable changes were made
to the outlook with this update. Isolated thunderstorms are developing/spreading eastward across the central Rockies this
afternoon -- ahead of a positively tilted midlevel trough moving
across the region. The strongest storms will be capable of producing
marginally severe hail and isolated severe gusts. For additional
details, see MCD #2047. Across the central Plains into the Upper MS
Valley, severe-thunderstorm potential is more uncertain along/behind
the cold front this evening into the overnight hours. However, given
the potential for isolated instances of severe hail and locally
strong/damaging gusts, the Marginal Risk has been maintained across
this area.

Farther east, clusters of thunderstorms are tracking westward across
the central Gulf Coast, in an environment characterized by 2+ inch
PW and pockets of diurnal heating/boundary-layer destabilization.
Given some banded convection here -- aided by enhanced low-level
easterlies -- a couple water-loaded downbursts will be possible.
Overall, the severe threat still appears too localized/marginal for
5-percent severe wind probabilities.

..Weinman.. 09/04/2024

.PREV DISCUSSION... /ISSUED 1124 AM CDT Wed Sep 04 2024/

...Central Rockies into the central High Plains...
Recent satellite imagery reveals a broad shortwave trough currently
moving through southern ID and northern NV/UT. This shortwave trough
and accompanying cold mid-level temperatures are forecast to
continue eastward throughout the day, progressing across WY and
northern CO. Modest buoyancy, fostered mainly by cooling mid-level temperatures, is anticipated across WY and adjacent parts of
northern CO as the shortwave trough progresses through. Thunderstorm development is expected as the large-scale ascent attendant to the
shortwave trough interacts with this buoyancy during the afternoon.
Moderate mid-level westerlies will accompany this shortwave trough
as well, with the resulting increase in vertical shear supporting
the potential for a few more organized/persistent storms. Initially
more cellular development across the higher terrain could pose a
risk for isolated hail, particularly across south-central WY and
north-central CO where the best overlap between the stronger shear
and cold mid-level temperatures is expected. Damaging wind gusts are
possible as well, particularly as the storms reach the lower
elevations of central High Plains where a deeply mixed boundary
layer will be in place.

...Central Plains into the Upper MS Valley...
Recent surface analysis places a low over southeast ND, with weak
troughing extending southwestward from this low in east-central CO.
The primary cold front is west of this surface trough, extending
from the low over southeast ND into more of northwest SD and
adjacent northeast WY. The surface low is forecast to progress east-southeastward throughout the day, reaching south-central MN by
late tonight. The attendant cold front is expected to push southward
during the same period, progressing through much of NE by early
Thursday morning.

Warm mid-level temperatures should preclude thunderstorm development
along the surface trough during the afternoon and evening. A few
isolated storms are possible during the evening behind the front as
the shortwave trough ejects out into the central Plains. Additional thunderstorm development is expected overnight/early Thursday
morning across the Upper MS Valley, with some isolated hail possible
within the strongest storms.

$$

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ACUS01 KWNS 050100
SWODY1
SPC AC 050058

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0758 PM CDT Wed Sep 04 2024

Valid 050100Z - 051200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PART OF
THE CENTRAL HIGH PLAINS NORTHEASTWARD INTO THE UPPER MISSISSIPPI
VALLEY...

...SUMMARY...
Isolated severe storms capable of damaging wind gusts and hail will
be possible this evening from parts of the central Rockies
northeastward into the upper Mississippi Valley.

...Central Rockies/Central Plains/Upper Mississippi Valley...
The latest water vapor imagery shows a positively-tilted upper-level
trough over the north-central Rockies, with west-southwesterly
mid-level flow over the northern Plains and upper Mississippi
Valley. At the surface, a cold front is located from eastern
Colorado northeastward into southwest Minnesota. Scattered
thunderstorms are ongoing behind the front from Colorado and Wyoming
eastward into the central High Plains. RAP analysis has weak
instability in place across the central High Plains and central
Rockies, with MLCAPE generally in the 250 to 500 J/kg range.
Forecast soundings across this weakly unstable airmass this evening
have 0-3 km shear mostly between 25 and 35 knots, with 850-500 mb
lapse rates near 7 C/km. This environment should be enough to
continue a marginal severe threat for a few more hours this evening.
Hail and isolated severe gusts will be the primary threats.

As the upper-level trough moves eastward this evening, large-scale
ascent will overspread parts of the northern Plains and upper
Mississippi Valley. Thunderstorms are expected to develop within and
near a pocket of moderate instability over eastern South Dakota,
northeastern Nebraska and southwest Minnesota. These storms could
also be associated with a potential for marginally severe wind gusts
and hail. The greatest threat should be with cells that develop near
the front late this evening, where instability is expected to be the
strongest.

..Broyles.. 09/05/2024

$$

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ACUS01 KWNS 050551
SWODY1
SPC AC 050550

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1250 AM CDT Thu Sep 05 2024

Valid 051200Z - 061200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTHEASTERN NEW MEXICO...

...SUMMARY...
Thunderstorms capable of severe wind gusts will be possible today
across part of northeastern New Mexico.

...Northeastern New Mexico...
A shortwave trough will move southward across the central Rockies
today. At the surface, a cold front will move southward into the
southern High Plains, as a lee trough develops and deepens across
northeastern New Mexico. As surface temperatures warm today near the
surface trough, a cluster of thunderstorms is expected to develop
ahead of a band of large-scale ascent. This cluster of storms is
expected to expand in size across southern Colorado and move
southward into northeastern New Mexico this afternoon. Ahead of the
cluster, surface dewpoints in the 50s F will contribute to weak destabilization. MLCAPE is expected to peak in the 500 to 750 J/kg
range by mid afternoon. RAP forecast soundings at 21Z in
northeastern New Mexico have 0-6 shear in the 25 to 30 knot range,
with 0-3 km lapse rates peaking in the 8.5 to 9 C/km range. This
should be sufficient for isolated severe wind gusts associated with
the stronger multicells. Hail will also be possible within the
stronger cores. The wind and hail threat should persist throughout
much of the afternoon as the storms gradually move southward from
northeastern New Mexico into east-central New Mexico.

..Broyles/Moore.. 09/05/2024

$$

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ACUS01 KWNS 051243
SWODY1
SPC AC 051242

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0742 AM CDT Thu Sep 05 2024

Valid 051300Z - 061200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
FAR SOUTH-CENTRAL COLORADO INTO NORTHERN/CENTRAL NEW MEXICO...

...SUMMARY...
Thunderstorms capable of producing isolated severe wind gusts and
hail will be possible today across parts of far south-central
Colorado into northern/central New Mexico.

...Central/Southern Rockies into the Southern High Plains...
On the southwest fringe of large-scale upper troughing over Canada
and the northern Plains/Upper Midwest, a mid-level shortwave trough
over the central Rockies this morning will move generally southward
across NM and vicinity through the day. Even though low-level
moisture remains fairly modest across the southern Rockies and
adjacent High Plains along/near of a cold front, cool mid-level
temperatures and somewhat steepened lapse rates aloft will likely
contribute to the development of around 500-750 J/kg of MLCAPE by
early afternoon as daytime heating occurs. Initial development of
robust convection by around 18-19Z will likely be tied to the higher
terrain as weak large-scale ascent associated with the shortwave
trough overspreads the south-central Rockies in a low-level
post-frontal regime. This activity should then spread generally south-southeastward across parts of northern/central NM through the
late afternoon and into the evening. While low-level easterly flow
ahead of the front is forecast to remain weak, veering winds with
height through mid/upper levels should still support around 25-35 kt
of effective bulk shear and some updraft organization. The strongest
cores that can develop may be capable of producing severe hail.
Otherwise, the threat for isolated strong to severe wind gusts
should spread southward in tandem with any small clusters that can
form.

...Great Lakes/Midwest to the Central Plains...
Generally elevated convection is ongoing this morning across parts
of the Upper Midwest along and near a surface cold front, and ahead
of a large-scale upper trough moving generally southeastward.
Instability across this region is expected to remain weak (MUCAPE
500 J/kg or less), which should tend to limit the overall severe
threat. Still, some of the stronger cores could produce small hail
or gusty winds in the short term. Other thunderstorms may eventually
develop this afternoon along/near the front across parts of the
Midwest and/or central Plains. Regardless, the overall severe threat
across these regions currently appears too limited to introduce low
severe probabilities.

..Gleason/Leitman.. 09/05/2024

$$

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ACUS01 KWNS 051625
SWODY1
SPC AC 051624

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1124 AM CDT Thu Sep 05 2024

Valid 051630Z - 061200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
FAR SOUTH-CENTRAL COLORADO INTO NORTHERN/CENTRAL NEW MEXICO...

...SUMMARY...
Thunderstorms capable of producing isolated severe wind gusts and
hail will be possible today across parts of far south-central
Colorado into northern/central New Mexico.

...Synopsis...
Satellite imagery shows a shortwave trough moving southeastward
through the central Rockies, between the upper ridging in place over
the western Great Basin and the broad upper troughing across central
Canadian and northern Plains/Upper MS Valley. Another shortwave
trough exists over the Upper MS Valley. This shortwave trough is
forecast to continue progressing eastward through the base broad
central Canada/northern Plains trough, moving across the Upper Great
Lakes and into eastern Ontario.

Recent surface analysis places a surface low associated with this
shortwave over Lake Superior, with a cold front extending
southwestward from this low through KS and into northeast NM. This
front is forecast to progress southward/southeastward as its parent
surface low lifts northeastward. Isolated thunderstorms are possible
along this frontal boundary, but overall severity should be
mitigated by modest buoyancy and vertical shear. Greater
thunderstorm coverage and severity is anticipated over the southern
Rockies as the previously mentioned central Rockies shortwave trough
continues southeastward and promotes thunderstorm development.

Lastly, a tropical wave just off the TX Coast is contributing to
abundant moisture across much of Gulf Coast, with low 70s dewpoints
reaching into much of east TX and northern LA, and upper 70s across
FL. Precipitable water values over 2" cover much of this region as
well. Heavy rain is the primary threat (as indicated by the latest
Day 1 Excessive Rainfall Outlook from WPC), but a few water-loaded
downbursts capable of damaging gusts are possible from southeast TX
and southern/central LA eastward along the Gulf Coast and over the
Florida Peninsula. Coverage of these gusts is expected to be sparse
and too low to delineate a 5% wind probability area.

...Southern Rockies/southern High Plains...
Moderate low-level moisture is anticipated within the post-frontal
airmass across the southern Rockies and adjacent southern High
Plains this afternoon, characterized by dewpoints in the low to mid
50s across the High Plains and upper 40s across the higher terrain.
Even with this modest moisture, the airmass is expected to
destabilize, fostered by deep boundary-layer mixing and cool
temperatures aloft (i.e. around -10 deg C at 500 mb). Surface easterlies/northeasterlies beneath modest westerlies aloft will
contribute to effective bulk shear around 35 kt, which is strong
enough for some updraft organization. Isolated hail is possible
across the higher terrain with the initially more cellular
development. Damaging gusts are expected to be the primary risk
thereafter as storms trend towards a more clustered mode and move
eastward into the more mixed southern High Plains.

..Mosier/Squitieri.. 09/05/2024

$$

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ACUS01 KWNS 051955
SWODY1
SPC AC 051953

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0253 PM CDT Thu Sep 05 2024

Valid 052000Z - 061200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
FAR SOUTH-CENTRAL COLORADO INTO NORTHERN/CENTRAL NEW MEXICO...

...SUMMARY...
Thunderstorms capable of producing isolated severe wind gusts and
hail will be possible today across parts of far south-central
Colorado into northern/central New Mexico.

...20Z Update...
The forecast remains on track, and with the exception of minor
trimming of General Thunder in parts of the Midwest (where
instability has weakened substantially), no appreciable changes were
made with this update. The severe threat will gradually increase
across portions of the southern Rockies and adjacent High Plains
through the afternoon, where isolated instances of hail and sporadic
severe wind gusts will be possible. For details, see MCD #2048.

..Weinman.. 09/05/2024

.PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Sep 05 2024/

...Synopsis...
Satellite imagery shows a shortwave trough moving southeastward
through the central Rockies, between the upper ridging in place over
the western Great Basin and the broad upper troughing across central
Canadian and northern Plains/Upper MS Valley. Another shortwave
trough exists over the Upper MS Valley. This shortwave trough is
forecast to continue progressing eastward through the base broad
central Canada/northern Plains trough, moving across the Upper Great
Lakes and into eastern Ontario.

Recent surface analysis places a surface low associated with this
shortwave over Lake Superior, with a cold front extending
southwestward from this low through KS and into northeast NM. This
front is forecast to progress southward/southeastward as its parent
surface low lifts northeastward. Isolated thunderstorms are possible
along this frontal boundary, but overall severity should be
mitigated by modest buoyancy and vertical shear. Greater
thunderstorm coverage and severity is anticipated over the southern
Rockies as the previously mentioned central Rockies shortwave trough
continues southeastward and promotes thunderstorm development.

Lastly, a tropical wave just off the TX Coast is contributing to
abundant moisture across much of Gulf Coast, with low 70s dewpoints
reaching into much of east TX and northern LA, and upper 70s across
FL. Precipitable water values over 2" cover much of this region as
well. Heavy rain is the primary threat (as indicated by the latest
Day 1 Excessive Rainfall Outlook from WPC), but a few water-loaded
downbursts capable of damaging gusts are possible from southeast TX
and southern/central LA eastward along the Gulf Coast and over the
Florida Peninsula. Coverage of these gusts is expected to be sparse
and too low to delineate a 5% wind probability area.

...Southern Rockies/southern High Plains...
Moderate low-level moisture is anticipated within the post-frontal
airmass across the southern Rockies and adjacent southern High
Plains this afternoon, characterized by dewpoints in the low to mid
50s across the High Plains and upper 40s across the higher terrain.
Even with this modest moisture, the airmass is expected to
destabilize, fostered by deep boundary-layer mixing and cool
temperatures aloft (i.e. around -10 deg C at 500 mb). Surface easterlies/northeasterlies beneath modest westerlies aloft will
contribute to effective bulk shear around 35 kt, which is strong
enough for some updraft organization. Isolated hail is possible
across the higher terrain with the initially more cellular
development. Damaging gusts are expected to be the primary risk
thereafter as storms trend towards a more clustered mode and move
eastward into the more mixed southern High Plains.

$$

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ACUS01 KWNS 060034
SWODY1
SPC AC 060033

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0733 PM CDT Thu Sep 05 2024

Valid 060100Z - 061200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE SOUTHERN ROCKIES...

...SUMMARY...
Thunderstorms capable of producing isolated severe wind gusts and
hail will remain possible through mid evening across parts of the
southern Rockies.

...01z Update...

Notable mid-level short-wave trough, currently located over southern
CO, is digging south-southeast in line with latest model guidance.
This feature is forecast to progress into southern NM by the end of
the period. Scattered robust convection has developed ahead of this
feature which has produced several severe wind gusts over the last
few hours. 00z sounding from ABQ exhibited a dry adiabatic lapse
rate in the lowest 3km, with steep mid-level lapse rates. While PW
values are not particularly high, adequate moisture is available for
efficient downbursts. Over the next few hours, scattered
strong/locally severe storms will propagate toward southern NM with
an attendant risk for severe gusts, or even marginally severe hail.
However, boundary-layer cooling should lead to weakening updrafts in
the next few hours and the severe threat will lessen markedly after
03-04z.

..Darrow.. 09/06/2024

$$

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ACUS01 KWNS 060536
SWODY1
SPC AC 060534

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1234 AM CDT Fri Sep 06 2024

Valid 061200Z - 071200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE OHIO
VALLEY REGION...

...SUMMARY...
Strong to locally severe storms are possible this afternoon across
much of Ohio and adjacent portions of the Great Lakes and Ohio
Valley.

...Ohio Valley Region...

Seasonally strong upper trough is currently located over
northwestern ON/upper MS Valley, digging southeast toward the Great
Lakes. Leading edge of strong 12hr mid-level height falls will
overspread the OH Valley this afternoon as a 500mb speed max
translates across MN/IA into northern IL/IN. Pronounced surface
front will advance into central OH, arcing southwest into western KY
by 18z, and this boundary will serve as the focus for potentially
robust convection this afternoon. Latest model guidance suggests
strong boundary-layer heating ahead of the front which should result
in SBCAPE in excess of 1000 J/kg as temperatures rise to near 80F.
Current thinking is scattered storms should readily develop by mid
day as convective temperatures are breached, aided by frontal
forcing. Modest 0-6km bulk shear suggests some potential for
organization, but lapse rates will not be that steep, and this
should limit updraft strength. Even so, some risk for locally
damaging winds, and perhaps some hail will exist with the strongest
storms. The primary window for severe will be between 06/18-07/00z.

..Darrow/Lyons.. 09/06/2024

$$

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ACUS01 KWNS 061247
SWODY1
SPC AC 061246

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0746 AM CDT Fri Sep 06 2024

Valid 061300Z - 071200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
OHIO TO THE OHIO VALLEY...

...SUMMARY...
Strong to locally severe storms are possible this afternoon from
Lake Erie across much of Ohio to the Ohio Valley.

...Synopsis...
A highly amplified mid/upper-level pattern will persist across the
CONUS, but with some weakening of the western mean ridge and
intensification of troughing over the Great Lakes/Ohio Valley
regions. The latter will occur in relation to a synoptic-scale
trough with several accompanying vorticity maxima and broad cyclonic
flow -- apparent in moisture-channel imagery over much of northern
ON and the Lake Superior vicinity. Phasing of accompanying
shortwaves/ vorticity lobes will contribute to both amplification
and wavelength shortening through the period. A closed 500-mb low
should develop around 00Z near the eastern end of Upper MI, with
trough near an MKG-ORD-MVN line. By 12Z, a fully developed cyclone
should cover much of ON from the southern end of James Bay to Lake
Erie, with 500-mb trough extending southwestward near a CVG-BNA
line. Associated cyclonic flow at that time will cover most of the
CONUS over and east of the mid/upper Mississippi Valley.

At the surface, a cold front related to the ON trough was drawn at
11Z near a DTW-FDY-IND-ICT line. This front should proceed eastward/southeastward across the Ohio Valley, Lower Great Lakes and
into the central/northern Appalachians through the period, ahead of
the mid/upper trough. By 00Z, the front should extend from Lake
Ontario across western parts of NY/PA to southeastern OH, northern
middle to western TN, and AR, becoming diffuse amidst northeast flow
on both sides over OK. Northeasterlies over the southern Plains
south of the cold front will be largely in isallobaric response to a
deepening surface frontal-wave low over the northwestern Gulf,
initially drawn about 100 nm south of GLS, and forecast to drift
erratically eastward through tonight. Strong/organized convection
related to the Gulf cyclone is expected to remain over water through
the period.

...OH, Ohio Valley...
Damaging to isolated, marginally severe gusts, as well as marginal
hail, will be possible with thunderstorms moving eastward across the
outlook area today.

A broken line of convection -- including widely scattered non-severe thunderstorms -- is apparent this morning from northwestern OH to
western MO approximately along the low-level cold front. This
activity, or succeeding/newer development after a short time gap
later this morning -- should become better organized between Lake
Erie and the Ohio Valley around midday as the foregoing boundary
layer (and prospective inflow) destabilizes. This will occur in
response to a combination of warm advection and diurnal heating/
mixing, whose mixing-related moisture-reduction effects will be
counterbalanced to some extent by moist advection. Activity should
move into a narrow corridor of 50s to mid 60s F surface dewpoints,
combining with diurnal heating to support patchy, highly variable
MLCAPE in the 500-1500 J/kg range.

Substantial westerly component to prefrontal near-surface flow will
limit both convergence and vertical shear, though weak MLCINH will
permit frontal development/maintenance of thunderstorms, regardless.
Around 30-35 kt effective-shear magnitudes will support mainly
multicells, though some intermittent/transient supercell character
will be possible for longer-lived, discrete cells. Activity should
weaken this evening as it moves eastward out of the most favorable
moisture, and into a nocturnally cooling/stabilizing boundary layer.

..Edwards/Kerr.. 09/06/2024

$$

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ACUS01 KWNS 061628
SWODY1
SPC AC 061627

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1127 AM CDT Fri Sep 06 2024

Valid 061630Z - 071200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM LAKE ERIE
ACROSS MUCH OF OHIO AND INTO SOUTHEAST INDIANA AND NORTHERN
KENTUCKY...

...SUMMARY...
Strong to locally severe storms are possible this afternoon from
Lake Erie across much of Ohio and into southeast Indiana and
northern Kentucky.

...Lower Great Lakes into the OH Valley...
Morning satellite imagery shows a well-defined shortwave trough
moving through the Upper Midwest and into the Mid MS/Lower OH
Valley. This shortwave trough is expected to continue
eastward/southeastward through OH Valley during the day, progressing
through the base of the parent upper trough over Ontario. Recent
surface analysis places the low associated with this wave over
southwestern Ontario. A cold front extends southwestward from this
low across the middle/lower OH Valley and the Ozark Plateau before
continuing through central and southwest OK.

Low-level airmass ahead of this front across much of the OH Valley
is characterized by mid 60s dewpoints. This low-level moisture is
forecast to advect northeastward into the Upper OH Valley in a
fairly narrow corridor ahead of the front throughout the day,
although boundary-layer mixing could drop dewpoints into the upper
50s by the afternoon. This low-level moisture will help support
modest buoyancy as the airmass diurnally warms, although the overall
buoyancy will be limited by both the boundary-layer mixing and
persistence of warm mid-level temperatures. There should still be
enough buoyancy to support thunderstorm development along the front
during the afternoon.

The stronger mid-level flow, and resultant stronger vertical shear,
will lag behind the front, while also having a more front-parallel
structure. This orientation, coupled with the modest buoyancy and
weak pre-frontal convergence, could result in quick undercutting of
any updrafts, leading to a more anafrontal character to the storms.
Even so, isolated thunderstorms may remain in the warm sector long
enough to produce a few damaging gusts. Isolated hail is possible as
well, even as storms become displaced behind the front. Activity
should weaken this evening as it moves eastward out of the most
favorable moisture, and into a nocturnally cooling/stabilizing
boundary layer.

...Elsewhere...
Isolated to widely scattered thunderstorms are possible along the
front from Mid-South vicinity across AR into northwest TX. Weak
buoyancy and shear should mitigate storm intensity, keeping the
severe potential low. Numerous thunderstorms are anticipated from
the Gulf Coast into FL, amid the tropical airmass in place. A few
water-loaded downbursts capable of damaging gusts are possible,
particularly across the FL Peninsula.

..Mosier/Dean.. 09/06/2024

$$

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ACUS01 KWNS 062000
SWODY1
SPC AC 061959

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Fri Sep 06 2024

Valid 062000Z - 071200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM LAKE ERIE
ACROSS MUCH OF OHIO AND INTO SOUTHEAST INDIANA AND NORTHERN
KENTUCKY...

...SUMMARY...
Strong to locally severe storms are possible this afternoon from
Lake Erie across much of Ohio and into southeast Indiana and
northern Kentucky.

...20Z Update...
Minimal changes were made to the outlook, as the previous forecast
remains on track. Along the front/wind shift in OH, a couple small,
loosely organized clusters (with transient supercell
characteristics) will be capable of producing strong to locally
damaging wind gusts through the afternoon, aided by diurnally
steepened low-level lapse rates. Isolated small to marginally severe
hail will also be possible with this activity. Farther southwest
into southeast IN, additional small clusters and weak/transient
left-movers are evolving behind the wind shift. Here, slightly
stronger deep-layer shear (per the latest IND VWP) could support
sporadic hail and isolated strong to severe gusts. Overall, the
severe threat still appears too marginal/localized for an upgrade.
For additional details on the near-term severe risk, see MCD #2049.

..Weinman.. 09/06/2024

.PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Sep 06 2024/

...Lower Great Lakes into the OH Valley...
Morning satellite imagery shows a well-defined shortwave trough
moving through the Upper Midwest and into the Mid MS/Lower OH
Valley. This shortwave trough is expected to continue
eastward/southeastward through OH Valley during the day, progressing
through the base of the parent upper trough over Ontario. Recent
surface analysis places the low associated with this wave over
southwestern Ontario. A cold front extends southwestward from this
low across the middle/lower OH Valley and the Ozark Plateau before
continuing through central and southwest OK.

Low-level airmass ahead of this front across much of the OH Valley
is characterized by mid 60s dewpoints. This low-level moisture is
forecast to advect northeastward into the Upper OH Valley in a
fairly narrow corridor ahead of the front throughout the day,
although boundary-layer mixing could drop dewpoints into the upper
50s by the afternoon. This low-level moisture will help support
modest buoyancy as the airmass diurnally warms, although the overall
buoyancy will be limited by both the boundary-layer mixing and
persistence of warm mid-level temperatures. There should still be
enough buoyancy to support thunderstorm development along the front
during the afternoon.

The stronger mid-level flow, and resultant stronger vertical shear,
will lag behind the front, while also having a more front-parallel
structure. This orientation, coupled with the modest buoyancy and
weak pre-frontal convergence, could result in quick undercutting of
any updrafts, leading to a more anafrontal character to the storms.
Even so, isolated thunderstorms may remain in the warm sector long
enough to produce a few damaging gusts. Isolated hail is possible as
well, even as storms become displaced behind the front. Activity
should weaken this evening as it moves eastward out of the most
favorable moisture, and into a nocturnally cooling/stabilizing
boundary layer.

...Elsewhere...
Isolated to widely scattered thunderstorms are possible along the
front from Mid-South vicinity across AR into northwest TX. Weak
buoyancy and shear should mitigate storm intensity, keeping the
severe potential low. Numerous thunderstorms are anticipated from
the Gulf Coast into FL, amid the tropical airmass in place. A few
water-loaded downbursts capable of damaging gusts are possible,
particularly across the FL Peninsula.

$$

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ACUS01 KWNS 070043
SWODY1
SPC AC 070042

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0742 PM CDT Fri Sep 06 2024

Valid 070100Z - 071200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe threat should be negligible the rest of tonight across the
Ohio Valley.

...01z Update...

Strong short-wave trough is digging southeast across the Great Lakes
early this evening. Large-scale ascent is spreading downstream ahead
of this feature, and this appears partly responsible for scattered
convection that developed along the associated cold front that
currently stretches from western NY-western PA-KY. Some of this
activity was briefly severe with gusts and some hail. However,
frontal convection is now spreading east of the primary instability
corridor where it will quickly encounter less favorable buoyancy.
Additionally, boundary-layer cooling will only lead to less
instability by mid evening. While gusty winds may continue with the
most robust storms for the next 1-2 hours, the overall severe threat
appears too limited to warrant MRGL risk overnight.

..Darrow.. 09/07/2024

$$

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ACUS01 KWNS 070548
SWODY1
SPC AC 070547

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1247 AM CDT Sat Sep 07 2024

Valid 071200Z - 081200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not forecast today; although, a
few strong gusts could accompany the most robust convection.

...Northeast...

Seasonally strong upper trough will shift across the lower Great
Lakes later this afternoon, along with 60-120m, 12hr 500mb height
falls. Latest guidance suggests a 70kt 500mb speed max will
translate through the base of the trough across eastern PA into
southern New England after 08/00z. This feature should encourage
scattered convection along the synoptic front, though mid-level
lapse rates are forecast to be quite weak, and this will limit
buoyancy across the Hudson Valley into northern NJ. Forecast
soundings ahead of the front suggest MLCAPE values will remain less
than 1000 J/kg, with only modest shear in the lowest 3km. While weak
frontal convection may exhibit some organization, given the
large-scale support, weak lapse rates and only modest
lower-tropospheric flow do not favor severe thunderstorms.

...Central High Plains...

Late-evening water-vapor imagery depicts a weak, but well-defined
short-wave trough over eastern MT, digging south-southeast toward
the Black Hills region. This feature will ensure a focused lee
trough holds across the central High Plains, and should encourage a strengthening LLJ this evening across western KS into western NE.
Latest model guidance suggests strong boundary-layer heating will
occur across eastern CO into the NE Panhandle. While convective
temperatures should be breached by late afternoon, PW values will
likely remain generally less than 1 inch across this region. Even
so, forecast soundings support high-based convection that will be
strongly sheared. Some consideration has been given for adding a
MRGL risk to portions of the NE Panhandle into northeast CO to
account for a few strong gusts, or perhaps marginally severe hail.
Will continue to monitor this region.

..Darrow/Lyons.. 09/07/2024

$$

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ACUS01 KWNS 071224
SWODY1
SPC AC 071223

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0723 AM CDT Sat Sep 07 2024

Valid 071300Z - 081200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not forecast today, though a few
strong gusts could accompany the most robust convection.

...Synopsis/Discussion...
The mid/upper-level pattern will feature strong, progressive
troughing over the Great Lakes and vicinity, and ridging from the
Four Corners north-northwestward to the Canadian Rockies. The major
synoptic trough over the Great Lakes is anchored by a cyclone
initially centered over Lake Huron. The low should move erratically
eastward to northeastward across ON to southwestern QC by the end of
the period. As this occurs, strengthening cyclonic flow and height
falls will overspread the Northeast, while cyclonic flow remains
behind the low across the Great Lakes, Ohio Valley and central
Appalachians.

An associated surface cold front -- analyzed at 11Z from central NY
across northwestern VA, easternmost TN, northern MS, north TX, and
central NM -- should move eastward across NY to central/eastern New
England by 00Z, extending southward offshore from most of the Mid-
Atlantic Coast, and merging with a northeastward-moving surface
cyclone now located offshore from SC. A separate surface cyclone
(with mid/upper-level extension) now south of Nova Scotia will move
northward, with peripheral isallobaric effects limiting convergence
along the cold front for much of today. Still, a band of showers
and embedded thunderstorms may organize enough to produce strong
gusts for a couple hours this afternoon from the Hudson Valley
region into NJ, the NYC area and western Long Island. At this time,
weak lapse rates and low-level shear are still forecast, and
organized severe-gust potential appears too low and conditional for
an outlook.

In the West, a weak binary cyclone (with two apparent centers in moisture-channel imagery) covers the coastal areas of OR and
northwestern CA, as well as adjoining Pacific waters. This feature
is devolving into an open-wave trough, and will continue to weaken
through the period as it slowly moves inland. Associated large-
scale ascent, overlapping diurnal/diabatic destabilization of higher
terrain, may contribute to thunder potential (including dry thunder
for fire-weather purposes) over portions of the interior Northwest.

Northwest flow aloft, east of the ridge, will overlie a well-
developed surface lee trough over eastern parts of CO/WY. Strong
veering with height is expected, but with weak low/middle-level
flow. Though ideally rich moisture will be well-removed from this
region, over the Gulf, enough residual/post-frontal moisture should
remain to support isolated to widely scattered, high-based
thunderstorms this afternoon over eastern WY/CO, and perhaps this
evening over southwestern NE near a strengthening LLJ. Forecast
soundings show a deep, well-mixed subcloud layer that may support
strong gusts from low-precip cells. However, with weak moisture and
strong mixing leading to limited buoyancy (MLCAPE less than 800
J/kg), severe potential appears isolated at best, with unconditional
areal probabilities remaining below 5% this outlook cycle.

..Edwards/Kerr.. 09/07/2024

$$

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ACUS01 KWNS 071632
SWODY1
SPC AC 071631

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1131 AM CDT Sat Sep 07 2024

Valid 071630Z - 081200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not forecast today, though a few
strong gusts could accompany the more intense storms.

...Northeast...
A cold front will move steadily east across the northeast today,
accompanied by showers and thunderstorms. Extensive cloud cover in
advance of the front will tend to limit heating/destabilization,
however modest MLCAPE (on the order of 250-500 J/kg) may develop
from the northern Delmarva Peninsula north into southeast NY this
afternoon. Ascent with an upper-level trough will continue to move
east in tandem with the front, and scattered thunderstorms may
develop this afternoon with some potential for locally gusty winds.
Weak instability and poor low-level lapse rates should limit severe
potential.

...Central High Plains...
Low-level moisture will be generally modest east of a surface trough
that will extend north-south across eastern portions of WY/CO this
afternoon. Still, lower 50s surface dew points and steep mid-level
lapse rates should contribute to MLCAPE of 750-locally near 1000
J/kg. Isolated thunderstorms may form and move southeast within a
northwest mid-level flow environment late this afternoon/evening,
and a deep/well-mixed boundary layer suggests some potential for
localized strong wind gusts. Thunderstorm potential may extend
eastward into western portions of NE/KS this evening as a low-level
jet strengthens. The overall coverage of any severe potential
remains too low to introduce severe probabilities.

...Interior Northwest...
The potential for isolated thunderstorms, already ongoing this
morning over south-central OR, will continue today as modest
large-scale ascent associated with a mid-level trough overspreads
inland areas of the Pacific Northwest. These storms may produce
limited rainfall, exacerbating fire weather concerns.

...Lower Colorado River Valley and Vicinity...
Strong heating will contribute to scattered thunderstorm development
this afternoon, and 12z hi-res guidance suggests that a couple of
stronger storms or small clusters may have the potential for gusty
outflow winds within a hot/well-mixed boundary layer.

..Bunting/Elliott.. 09/07/2024

$$

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ACUS01 KWNS 071939
SWODY1
SPC AC 071938

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0238 PM CDT Sat Sep 07 2024

Valid 072000Z - 081200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not forecast today, though a few
strong gusts could accompany the more robust storms.

...20Z Update...
The forecast remains on track, and only minor changes were made to
the outlook with this update. In particular, the General Thunder
line was trimmed behind the frontal rain band and associated wind
shift in the Northeast, where cool post-frontal conditions have
generally depleted instability. Updrafts within this band have
remained too shallow/weak for an appreciable lightning risk thus
far. However, an isolated strike still cannot be ruled out,
especially over portions of eastern NJ and far southeastern NY/Long
Island -- where filtered boundary-layer heating has occurred amid
middle 60s dewpoints. Isolated/embedded strong gusts also remain
possible (earlier 44 mph gust in eastern PA), though the
weak/shallow updrafts (and associated downdrafts) should continue to
limit the severe risk.

Elsewhere, severe potential still appears too localized and/or
marginal for severe probabilities. See the previous discussion below
for details.

..Weinman.. 09/07/2024

.PREV DISCUSSION... /ISSUED 1131 AM CDT Sat Sep 07 2024/

...Northeast...
A cold front will move steadily east across the northeast today,
accompanied by showers and thunderstorms. Extensive cloud cover in
advance of the front will tend to limit heating/destabilization,
however modest MLCAPE (on the order of 250-500 J/kg) may develop
from the northern Delmarva Peninsula north into southeast NY this
afternoon. Ascent with an upper-level trough will continue to move
east in tandem with the front, and scattered thunderstorms may
develop this afternoon with some potential for locally gusty winds.
Weak instability and poor low-level lapse rates should limit severe
potential.

...Central High Plains...
Low-level moisture will be generally modest east of a surface trough
that will extend north-south across eastern portions of WY/CO this
afternoon. Still, lower 50s surface dew points and steep mid-level
lapse rates should contribute to MLCAPE of 750-locally near 1000
J/kg. Isolated thunderstorms may form and move southeast within a
northwest mid-level flow environment late this afternoon/evening,
and a deep/well-mixed boundary layer suggests some potential for
localized strong wind gusts. Thunderstorm potential may extend
eastward into western portions of NE/KS this evening as a low-level
jet strengthens. The overall coverage of any severe potential
remains too low to introduce severe probabilities.

...Interior Northwest...
The potential for isolated thunderstorms, already ongoing this
morning over south-central OR, will continue today as modest
large-scale ascent associated with a mid-level trough overspreads
inland areas of the Pacific Northwest. These storms may produce
limited rainfall, exacerbating fire weather concerns.

...Lower Colorado River Valley and Vicinity...
Strong heating will contribute to scattered thunderstorm development
this afternoon, and 12z hi-res guidance suggests that a couple of
stronger storms or small clusters may have the potential for gusty
outflow winds within a hot/well-mixed boundary layer.

$$

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ACUS01 KWNS 080036
SWODY1
SPC AC 080036

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0736 PM CDT Sat Sep 07 2024

Valid 080100Z - 081200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not forecast today, though a few
strong gusts could accompany the more robust storms across the
central High Plains and Lower Colorado River Valley vicinity.

...01Z Update...

...Northeast...
General thunder was removed across the region given the scant
buoyancy and limited land area ahead of the cold front across
southern New England. A flash or two is still possible within the
more cellular activity across western NY and PA. However, coverage
is expected to be less than 10%.

...Elsewhere...
Isolated thunderstorms remain possible along the immediate Gulf
Coast and across the FL Peninsula tonight through tomorrow morning.
Isolated to widely scattered thunderstorm are expected to continue
from the central High Plains/central Rockies through much of AZ and
the Lower CO River Valley. Highest coverage is expected over the
Lower CO River Valley. A few stronger storms capable of hail and/or
damaging wind gusts in these areas, but overall coverage should
remain very isolated. Lastly, isolated thunderstorms could last a
few more hour across central OR and adjacent south-central WA.

..Mosier.. 09/08/2024





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ACUS01 KWNS 080549
SWODY1
SPC AC 080547

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1247 AM CDT Sun Sep 08 2024

Valid 081200Z - 091200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The organized severe-thunderstorm threat is expected to be low on
Sunday.

...Synopsis and Discussion...
A mature mid-latitude cyclone, embedded within larger upper
troughing, is forecast to progress northeastward from southern
Quebec into northeastern Quebec. Another shortwave trough is
expected to move through the western portion of the parent upper
troughing, dropping across western Ontario and the Upper Great Lakes
Sunday evening into Monday morning. Isolated thunderstorms are
possible with this second wave late Sunday night into early Monday
morning. Evolution of these shortwaves will help maintain troughing
across much of the eastern CONUS throughout the period.

Farther west, upper ridging will gradually move eastward into the
Plains while a low-amplitude shortwave trough moves through the
Pacific Northwest and into the northern Rockies.

At the surface, expansive high pressure centered over the Mid MS
Valley will dominate the sensible weather from the Mid MS and OH
Valleys into much of the central and southern Plains. This should
keep any low-level moisture confined to the immediate Gulf Coast and
FL Peninsula. A stationary front will likely extend from a low over
the far western Gulf of Mexico northeastward through northern FL.
Thunderstorms are possible in the vicinity of this boundary
throughout the day, with the highest coverage expected over the northern/central FL Peninsula. Abundant cloud cover will limit
heating across northern/central FL Peninsula, and lapse rates will
be poor. However, mid-level flow around 40 kt may support enough
vertical shear for a few more persistent/organized updrafts capable
of damaging gusts. Even so, severe coverage is expected to remain
less than 5%.

Afternoon thunderstorms are expected again from the central High
Plains into parts of the central/southern Rockies, Great Basin, and
Southwest. High-based character of these storms could result in a
few locally strong gusts. Isolated high-based thunderstorms are also
possible from the interior Pacific Northwest into the northern
Rockies as a shortwave trough progresses through the region. A few
strong gusts are possible with these storms as well. In both of
these areas, overall severe coverage is expected to remain less than
5%.

..Mosier/Lyons.. 09/08/2024

$$

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ACUS01 KWNS 081225
SWODY1
SPC AC 081224

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0724 AM CDT Sun Sep 08 2024

Valid 081300Z - 091200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Though a few strong thunderstorm gusts may be noted in the interior
Northwest and central High Plains, severe potential appears too low
and disorganized for an outlook area.

...Synopsis/Discussion...
In mid/upper levels, the large-scale pattern will deamplify somewhat
over the CONUS this period, but maintain a mean trough in the Great
Lakes and eastern CONUS, and mean ridging over the Intermountain
West and Southwestern deserts. A shortwave trough -- evident in moisture-channel imagery over the interior of OR/WA into far
northern CA -- is forecast to continue weakening as it moves
northeastward, crossing the northern Rockies between 06-12Z. Still,
associated cooling aloft and midlevel moisture, over pockets of
marginally favorable low-level moisture and diurnal surface heating,
will contribute to general thunderstorm potential in parts of the
interior Northwest and Intermountain West. A few of these high-
based cells may produce strong gusts, but severe potential appears
to be limited by lack of greater moisture/buoyancy.

Farther east over the central Rockies and adjoining High Plains,
isolated to widely scattered thunderstorms are possible this
afternoon into evening. Activity should be related to diabatic
heating of elevated terrain, along with lift near a surface lee
trough, and a corridor of meager but sufficient low-level moisture.
Beneath strongly difluent but weak west to northwest flow in mid/
upper levels, bulk shear should be modest, despite considerable
veering with height. Here too, a few cells may produce strong gusts
through a well-mixed subcloud layer, and a severe gust cannot be
ruled out. However, severe potential appears too isolated, poorly
focused and conditional for a categorical risk area. Elsewhere,
isolated to scattered thunderstorms will be possible in a very moist
air mass (but with poor lapse rates) from parts of the Gulf Coast
States across FL and the southern Atlantic Coast.

..Edwards/Kerr.. 09/08/2024

$$

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ACUS01 KWNS 081618
SWODY1
SPC AC 081616

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1116 AM CDT Sun Sep 08 2024

Valid 081630Z - 091200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms appear unlikely through tonight.

...Synopsis and Discussion...
Recent surface observations show a nearly stalled front over north
FL. Daytime heating of a moist low-level airmass south of this
boundary will likely encourage the development of scattered to
numerous thunderstorms this afternoon over the northern and central
FL Peninsula. While occasional strong/gusty winds may occur with any downdrafts, the presence of poor mid-level lapse rates should hinder
updraft acceleration and overall convective intensity.

Even with upper ridging remaining prominent over much of the West,
high-based convection may develop this afternoon over the
southern/central Rockies, and perhaps into the adjacent High Plains
along/near a weak lee surface trough. Limited low-level moisture and
generally weak effective bulk shear over these regions will likely
preclude an organized severe threat, although strong winds may occur
with any convection that can be sustained.

Water vapor satellite imagery shows a mid-level shortwave trough
over the Pacific Northwest this morning. This feature will move
generally east-northeastward towards the northern Rockies through
the period. Isolated thunderstorms may occur across interior
portions of the Northwest this afternoon ahead of the shortwave
trough. But, rather modest low-level moisture (surface dewpoints
generally in the 30s/40s F) should hinder the development of any
more than weak instability. Along with only modestly enhanced
mid-level flow, the limited instability is expected to keep any
severe wind threat with convective downdrafts across eastern WA/OR
into ID and northern NV/UT quite sparse.

..Gleason/Halbert.. 09/08/2024

$$

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ACUS01 KWNS 081944
SWODY1
SPC AC 081942

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0242 PM CDT Sun Sep 08 2024

Valid 082000Z - 091200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms appear unlikely through tonight.

...20Z Update...
The forecast remains on track, and no changes/additions were needed
to the outlook with this update. In addition to the low-end/
localized convective concerns described below, a couple dry
microbursts could accompany high-based thunderstorms developing over
the higher terrain in portions of Southern CA this afternoon. While
weak deep-layer flow/shear will limit thunderstorm
organization/longevity here, a hot/deeply mixed boundary layer
(temperatures around 100 F), and lower/middle 50s F dewpoints will
still favor a few robust (albeit short-lived) storms capable of
locally strong gusts.

..Weinman.. 09/08/2024

.PREV DISCUSSION... /ISSUED 1116 AM CDT Sun Sep 08 2024/

...Synopsis and Discussion...
Recent surface observations show a nearly stalled front over north
FL. Daytime heating of a moist low-level airmass south of this
boundary will likely encourage the development of scattered to
numerous thunderstorms this afternoon over the northern and central
FL Peninsula. While occasional strong/gusty winds may occur with any downdrafts, the presence of poor mid-level lapse rates should hinder
updraft acceleration and overall convective intensity.

Even with upper ridging remaining prominent over much of the West,
high-based convection may develop this afternoon over the
southern/central Rockies, and perhaps into the adjacent High Plains
along/near a weak lee surface trough. Limited low-level moisture and
generally weak effective bulk shear over these regions will likely
preclude an organized severe threat, although strong winds may occur
with any convection that can be sustained.

Water vapor satellite imagery shows a mid-level shortwave trough
over the Pacific Northwest this morning. This feature will move
generally east-northeastward towards the northern Rockies through
the period. Isolated thunderstorms may occur across interior
portions of the Northwest this afternoon ahead of the shortwave
trough. But, rather modest low-level moisture (surface dewpoints
generally in the 30s/40s F) should hinder the development of any
more than weak instability. Along with only modestly enhanced
mid-level flow, the limited instability is expected to keep any
severe wind threat with convective downdrafts across eastern WA/OR
into ID and northern NV/UT quite sparse.

$$

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ACUS01 KWNS 090047
SWODY1
SPC AC 090045

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0745 PM CDT Sun Sep 08 2024

Valid 090100Z - 091200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are unlikely through tonight.

...01z Update...
Evening water vapor imagery shows a prominent mid-level ridge
remains in place over much of the CONUS, with surface high pressure
favoring dry and quiescent weather over much of the country. To the
east of the ridge, an upper low over the Northeast and eastern
Canada is slowly filling. A cold front trailing south of the low has
moved mostly offshore, but was supporting scattered showers and
thunderstorms in the northern Gulf of Mexico and across parts of FL.
Continued offshore flow ahead of the surface high moving slowly
south and east should keep much of this activity offshore or
confined to the immediate coast through the next 12 hours. Storms
should gradually diminish in coverage and intensity through the
remainder of the evening.

To the west, weak and broader troughing is ongoing over the West
Coast with an embedded shortwave perturbation crossing the northern
Rockies. Monsoon moisture advection ahead of theses features is
supporting scattered thunderstorms across much of the Intermoutnain
West, into the northern Rockies and across much of the Desert
Southwest. Scattered showers and thunderstorms appear likely to
persist into this evening as the weak trough shifts slowly eastward,
especially across parts of ID and the Great Basin where more
clustering has occurred. Storms are predominately high-based in
nature, owing to steep low-level lapse rates, hot temperatures and
the limited monsoon moisture. This could support an occasional dry
downburst with the more robust cores, mainly over parts of southern
CA. However, limited deep-layer shear and weak overall buoyancy
suggests these storms are unlikely to be meaningfully organized or
persistent. Thus, will continue with severe probs less than 5%.
Storms should begin to decrease in coverage this evening with the
loss of diurnal heating and mid-level drying. Otherwise, the severe
risk appears limited across much of the country.

..Lyons.. 09/09/2024

$$

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ACUS01 KWNS 090552
SWODY1
SPC AC 090550

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1250 AM CDT Mon Sep 09 2024

Valid 091200Z - 101200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE EASTERN GREAT LAKES VICINITY...

...SUMMARY...
Thunderstorms will be possible today over parts of the eastern Great
Lakes, along the Gulf Coast, and from the Four Corners northward
into the northern Plains. Isolated storms may produce damaging wind
gusts over western and central New York State.

...Synopsis...
A large upper ridge will remain in place over the Central CONUS
flanked by broad trouging to the west and a lingering upper low over
eastern Canada. Behind the upper low, a secondary embedded shortwave
trough and speed max are forecast to move south out of western
Ontario and over the Great Lakes, providing adequate lift for
scattered thunderstorms over parts of the Northeast. To the west,
scattered thunderstorms are likely over the Great Basin into the
Four Corners, with a few thunderstorms possible over the Northern
Plains ahead of the western US trough. Finally, scattered
thunderstorms may also develop by afternoon peak heating along the
Gulf Coast into FL and near the outer bands of PTC6.

...Great Lakes vicinity...
As the aforementioned mid-level speed max approaches from southern
Canada, shower and thunderstorm activity should begin to increase in
coverage and intensity in the vicinity of Lakes Erie/Ontario, as
well as over portions of northwestern NY State by mid morning.
Limited, but adequate, surface moisture (dewpoints in the mid 50s to
near 60 F), combined with daytime heating, and 500 mb temps of -18
to -20C will support weak destabilization (MLCAPE 500-700 J/kg)
across parts of the lower Great Lakes and Northeast. Low-topped
bands or clusters of predominately multicell storms are likely, and
may briefly organize owing to increasing flow aloft aiding
deep-layer shear to near 30 kt. Despite the weak buoyancy, fairly
steep low-level lapse rates (~7 C/km) beneath the upper low, may
support a few damaging gusts and instances of small hail with the
strongest storms through the afternoon. Convection should eventually
outrun the more robust buoyancy and weaken to the southeast into
parts of northern PA and southern New England this evening.

..Lyons.. 09/09/2024

$$

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ACUS01 KWNS 091240
SWODY1
SPC AC 091239

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0739 AM CDT Mon Sep 09 2024

Valid 091300Z - 101200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN PARTS OF NEW
YORK...

...SUMMARY...
Isolated damaging thunderstorm gusts are possible in parts of New
York.

...Synopsis...
Mid/upper-level flow will become more zonal across most of the
northwestern and north-central CONUS, as a series of embedded
shortwave troughs penetrates/flattens antecedent ridging over the
Intermountain West and central/northern Rockies. Downstream, a
substantial cyclone -- initially centered near the southwestern edge
of Labrador -- anchors mean troughing that extends southwestward
down the Appalachians. The cyclone will eject northeastward over
Labrador through the period. In its southwestern quadrant, a
shortwave trough was apparent in moisture-channel imagery over
northeastern ON, approaching Georgian Bay and the neck of ON. This
feature should move southeastward to the upper St. Lawrence Valley,
eastern Lake Ontario and western NY by 00Z, then across southern New
England and offshore from the northern Mid-Atlantic Coast overnight.

The 11Z surface analysis showed a weak cold front from southern QC,
through a frontal-wave low over northern Lake Huron, then across
northern parts of WI/MN. The low should move east-southeastward
toward Lake Ontario and weaken through the day, while the cold front
and associated veering wind shift cross the remainder of ON and
start moving into NY. The front should cross the remainder of NY
and most of New England and PA overnight. An older, quasistationary
front was drawn across north-central FL westward over north-central
Gulf shelf waters, then bending southwestward into the western parts
of the developing tropical cyclone in the western Gulf.

Potential TC 6 -- now offshore from the Mexican Gulf Coast -- is
forecast by NHC to organize into a tropical storm this period.
Given the forecast track, intensity and wind radii, any developing
favorable sector for supercells/tornadoes will remain well out in
the Gulf day-1, and not an overland tornado concern until day 3,
when a risk area has been introduced northeast/east of the forecast
center track. See NHC advisories on this system for latest tropical watches/warnings, and path/strength forecasts.

...NY...
Widely scattered to scattered thunderstorms are expected to move
southeastward to eastward across the outlook area from early
afternoon into early evening. Isolated damaging gusts, and perhaps
a gust or two near severe limits, may occur from the most vigorous
embedded cells.

This convection will be related to a compact (mesoscale) but strong
field of large-scale ascent preceding the shortwave trough, related
to its progressive field of DCVA, and forcing in the left-exit
region of a cyclonically curved speed max in the 250-500-mb layer.
The UVV field likely is manifest already by convection now over
Georgian Bay and vicinity, moving toward what should become a more
unstable environment over the outlook area. Deep-layer mean lapse
rates likely will never get steeper than about 6.5 C/km in this
setting. Still, the combination of subtle cooling aloft, weak but
sufficient boundary-layer moisture, and some diurnal heating ahead
of the UVV field, should deepen the buoyant layer enough to yield
pockets of 500-700 J/kg MLCAPE. Weak low-level shear, and 25-30 kt effective-shear magnitudes in forecast soundings, indicate activity
should be multicellular. A shallow but well-mixed subcloud layer --
containing around 7 C/km lapse rates -- will support strong
downdraft accelerations in some of the cores.

..Edwards/Kerr.. 09/09/2024

$$

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ACUS01 KWNS 091628
SWODY1
SPC AC 091626

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1126 AM CDT Mon Sep 09 2024

Valid 091630Z - 101200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
NEW YORK...

...SUMMARY...
Isolated damaging winds may occur this afternoon across parts of New
York.

...New York...
Within large-scale upper troughing over the Northeast and eastern
Canada, an embedded shortwave trough over southern Ontario and the
upper Great Lakes will continue to move across the Northeast this
afternoon and evening. Ascent associated with this shortwave trough
and related mid-level jet is supporting isolated thunderstorms
across southern Ontario and vicinity. This activity will spread east-southeastward this afternoon across parts of NY. The airmass
over this region should become only weakly unstable as filtered
daytime heating occurs, with poor mid-level lapse rates, persistent
cloud cover, and modest low-level moisture limiting destabilization.
Still, gradually increasing west-northwesterly winds at low/mid
levels will foster around 25-35 kt of deep-layer shear. This should
support modest thunderstorm organization, with multicells/small
clusters potentially evolving along and downstream of Lake Ontario.
Isolated strong to damaging winds should be the main threat with
this convection as it moves across much of NY this afternoon and
early evening, before eventually weakening with eastward extent with
the loss of daytime heating.

...Northern/Central Rockies and High Plains...
Isolated to widely scattered thunderstorms should develop this
afternoon over portions of the northern/central Rockies as a weak
shortwave trough continues eastward. Low-level moisture and related
instability are both expected to remain rather meager into the High
Plains, which should limit updraft intensities. Still, isolated
strong/gusty winds may occur with this high-based activity across
parts of MT/WY where low-level lapse rates can become steepened.
Greater low-level moisture is present farther east into the Dakotas,
along/east of a weak surface low/trough. But, increasing
low/mid-level temperatures and a strong cap should generally inhibit thunderstorm development through much of the day with eastward
extent across the northern/central Plains.

..Gleason/Halbert.. 09/09/2024

$$

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ACUS01 KWNS 091936
SWODY1
SPC AC 091934

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0234 PM CDT Mon Sep 09 2024

Valid 092000Z - 101200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF NEW
YORK...

...SUMMARY...
Isolated damaging winds remain possible this afternoon across parts
of New York.

...20Z Update...
No changes have been made to the Day 1 Convective Outlook. With
storms continuing to increase in coverage and intensity over western
NY, atop marginal boundary-layer-based instability, an instance or
two of damaging gusts remain possible with one of the stronger
storms. Similarly, a severe gust cannot be ruled out with one of the
stronger storms over the Interior West given the presence of steep
tropospheric lapse rates. Please see the previous outlook (below)
for more details.

..Squitieri.. 09/09/2024

.PREV DISCUSSION... /ISSUED 1126 AM CDT Mon Sep 09 2024/

...New York...
Within large-scale upper troughing over the Northeast and eastern
Canada, an embedded shortwave trough over southern Ontario and the
upper Great Lakes will continue to move across the Northeast this
afternoon and evening. Ascent associated with this shortwave trough
and related mid-level jet is supporting isolated thunderstorms
across southern Ontario and vicinity. This activity will spread east-southeastward this afternoon across parts of NY. The airmass
over this region should become only weakly unstable as filtered
daytime heating occurs, with poor mid-level lapse rates, persistent
cloud cover, and modest low-level moisture limiting destabilization.
Still, gradually increasing west-northwesterly winds at low/mid
levels will foster around 25-35 kt of deep-layer shear. This should
support modest thunderstorm organization, with multicells/small
clusters potentially evolving along and downstream of Lake Ontario.
Isolated strong to damaging winds should be the main threat with
this convection as it moves across much of NY this afternoon and
early evening, before eventually weakening with eastward extent with
the loss of daytime heating.

...Northern/Central Rockies and High Plains...
Isolated to widely scattered thunderstorms should develop this
afternoon over portions of the northern/central Rockies as a weak
shortwave trough continues eastward. Low-level moisture and related
instability are both expected to remain rather meager into the High
Plains, which should limit updraft intensities. Still, isolated
strong/gusty winds may occur with this high-based activity across
parts of MT/WY where low-level lapse rates can become steepened.
Greater low-level moisture is present farther east into the Dakotas,
along/east of a weak surface low/trough. But, increasing
low/mid-level temperatures and a strong cap should generally inhibit thunderstorm development through much of the day with eastward
extent across the northern/central Plains.

$$

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ACUS01 KWNS 100034
SWODY1
SPC AC 100033

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0733 PM CDT Mon Sep 09 2024

Valid 100100Z - 101200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected this evening and overnight.

...01Z Update...
The overall severe threat across NY continues to decrease as the
airmass stabilizes. Isolated thunderstorms will continue, but the
reduced severe threat merits removal of the severe probabilities.

Isolated thunderstorms will also remain possible from the Great
Basin into the central Rockies/central High Plains this evening,
before expanding eastward/northeastward into the central Plains and
Mid MO Valley overnight into Wednesday morning.

Lastly, thunderstorms will remain possible along the Gulf Coast and
FL Peninsula. Highest coverage is anticipated across the TX Coast as
rainbands associated TC Francine move across the region. Severe
potential within these bands is expected to be very low.

..Mosier.. 09/10/2024

$$

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ACUS01 KWNS 100534
SWODY1
SPC AC 100533

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1233 AM CDT Tue Sep 10 2024

Valid 101200Z - 111200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE LA
COAST...

...SUMMARY...
Some tornado threat associated with Tropical Cyclone Francine may
approach the Louisiana Coast by early Wednesday morning.

...Synopsis...
A shortwave trough is expected to be off the Northeast Coast early
Tuesday morning, with continued eastward progression into the
northern Atlantic expected thereafter. A relatively zonal pattern is anticipated west of this shortwave trough across the majority of the
CONUS throughout much of the period. A low-amplitude shortwave
trough is forecast to move within this zonal flow across the
northern Plains and the Upper Midwest, but with minimal pattern
amplification. Some amplification is expected late Tuesday/early
Wednesday across the Pacific Northwest, ahead of a strong shortwave
trough approaching the coast.

Surface pattern early Tuesday will feature high pressure centered
over the central Appalachians and covering much of the OH Valley.
This ridging is expected to gradually shift eastward/northeastward
throughout the period. Surface troughing associated with the
northern Plains shortwave trough will extend across the central
Dakotas early Tuesday, before then shifting eastward throughout the
day. Farther south across the northwest Gulf of Mexico, TC Francine
is expected to reach hurricane strength while gradually progressing northeastward.

...TC Francine - LA Coast...
Rainbands from Francine will likely spread across the northwest Gulf
Coast throughout the day, but the stronger flow will remain
displaced south throughout much of the period. Beginning around 06Z,
the stronger flow may be far enough north to influence any deeper
updrafts that develop along the LA Coast, with an attendant risk for
brief tornadoes.

...Upper Midwest...
Moderate low-level moisture, characterized by surface dewpoints in
the upper 50s/low 60s, is expected across the region Tuesday
afternoon ahead of the approaching shortwave trough and associated
surface trough. Steep mid-level lapse rates will aid in the
development of strong buoyancy across the region, supporting a
conditional severe-thunderstorm risk. However, despite moderate
low-level moisture and strong daytime heating, warm mid-level
temperatures are forecast to keep capping in place, precluding
afternoon thunderstorm development.

...Elsewhere...
Afternoon thunderstorms are expected again across the eastern Great
Basin and northern/central Rockies, where orographic effects and
modest large-scale ascent will combine with modest moisture and
buoyancy to support thunderstorm development. Increasing
thunderstorm potential is anticipated late Tuesday into early
Wednesday across the Pacific Northwest ahead of the approaching
shortwave trough.

..Mosier/Lyons.. 09/10/2024

$$

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ACUS01 KWNS 101244
SWODY1
SPC AC 101243

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0743 AM CDT Tue Sep 10 2024

Valid 101300Z - 111200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER COASTAL
AREAS OF LOUISIANA...

...SUMMARY...
Marginal tornado potential may reach coastal areas of Louisiana
during the late overnight/early morning hours.

...Synopsis...
In mid/upper levels, a strong shortwave trough now over the eastern
Gulf of Alaska is forecast to dig southeastward and develop a closed
500-mb cyclone tonight, with the low about 150 nm west of AST by 12Z
tomorrow. Ahead of this progressive and intensifying perturbation,
height falls and strengthening cyclonic flow will spread across the northwestern CONUS throughout the period, combining with modest low/ middle-level moisture to support thunderstorm potential in parts of
the Northwest, in addition to the diurnal-cycle convection across
the Four Corners region, central/northern Rockies and parts of MT.

Downstream, mid/upper flow should be nearly zonal from the Rockies
across the Great Lakes. An embedded shortwave trough was evident in moisture-channel imagery over the Dakotas. This feature is forecast
to move eastward to MN by 00Z, then across the Upper Great Lakes to
Lake Huron and adjoining parts of ON by 12Z. Farther south, a weak,
cut-off, mid/upper-level low over north-central TX should drift
erratically near its present location, while increasingly
influencing the path of Tropical Storm Francine.

The 11Z surface analysis showed a wavy, quasistationary frontal zone
fro Atlantic waters offshore SC, across northern FL to near the
Mississippi River mouth, then a warm front arching across Gulf
waters just south of the LA and TX Coasts, and into western parts of
the Francine circulation. This boundary should move little from
about 90W eastward, but remain a warm front over the upper TX and LA
coastal waters, diffusely shifting inland over southern LA through
the period.

...LA Coast...
T.S. Francine -- initially centered southeast of BRO -- is forecast
by NHC to turn northeastward across the northwestern Gulf today and
become a hurricane, then move ashore in Louisiana on day 2.
Suitably rich low-level moisture already is in place over coastal
LA, and scattered to numerous showers and thunderstorms should cover
the outlook area throughout much of the period, even well northeast
of Francine's center. However, supercell potential will await
sufficiently strong wind fields reaching the coastline ahead of the
cyclone to enlarge hodographs favorably -- likely during the last
few hours of the period. Then, tornado potential will be a matter
of having relatively distinct/discrete, outer-band convection that
can survive long enough to mature into supercells before weakening
again in more-stable inflow air -- either inland or in broader
precip areas. Unconditional probabilities are kept at marginal
levels for now, given the late timing of the favorable kinematic
fields, the nocturnal min in overland instability, and convective/
structural uncertainties with Francine.

..Edwards/Kerr.. 09/10/2024

$$

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ACUS01 KWNS 101624
SWODY1
SPC AC 101622

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1122 AM CDT Tue Sep 10 2024

Valid 101630Z - 111200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF COASTAL/SOUTHEAST LOUISIANA...

...SUMMARY...
Marginal tornado potential may reach coastal areas of Louisiana
during the late overnight/early morning hours.

...Southern Louisiana Late Tonight/Early Wednesday Morning...
The latest NHC forecast indicates Tropical Cyclone Francine will
move northeastward over the western Gulf of Mexico tonight through
early Wednesday morning. Morning surface observations show a stalled
front remains situated over the northern Gulf, with greater
low-level moisture (mid/upper 70s surface dewpoints) generally
confined near or just off the LA/MS/AL Gulf Coast. As Francine
approaches the LA Coast late tonight, this very moist low-level
airmass over the northern Gulf should gradually spread inland along
parts of the immediate central Gulf Coast, supporting weak
boundary-layer instability. As Francine approaches, a corresponding
increase in low-level flow and related effective SRH should support
some threat for tornadoes with any low-topped supercells in outer
rain bands to the east-northeast of the central circulation. Latest
guidance continues to suggest that the better tornado potential over
land will occur in the Day 2/Wednesday time frame (after 12Z). But,
an isolated/marginal tornado threat still remains apparent along
parts of the LA Coast for the last few hours of the Day 1 period
(08-12Z) early Wednesday morning, where a Marginal Risk has been
maintained.

..Gleason/Bentley.. 09/10/2024

$$

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ACUS01 KWNS 101942
SWODY1
SPC AC 101940

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0240 PM CDT Tue Sep 10 2024

Valid 102000Z - 111200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF COASTAL/SOUTHEAST LOUISIANA...

...SUMMARY...
Marginal tornado potential may reach coastal areas of Louisiana
during the late overnight/early morning hours.

...20z Update...
The forecast remains on track and no changes are needed to the D1
Convective Outlook. See previous discussion below for more
information.

..Thornton/Gleason.. 09/10/2024

.PREV DISCUSSION... /ISSUED 1122 AM CDT Tue Sep 10 2024/

...Southern Louisiana Late Tonight/Early Wednesday Morning...
The latest NHC forecast indicates Tropical Cyclone Francine will
move northeastward over the western Gulf of Mexico tonight through
early Wednesday morning. Morning surface observations show a stalled
front remains situated over the northern Gulf, with greater
low-level moisture (mid/upper 70s surface dewpoints) generally
confined near or just off the LA/MS/AL Gulf Coast. As Francine
approaches the LA Coast late tonight, this very moist low-level
airmass over the northern Gulf should gradually spread inland along
parts of the immediate central Gulf Coast, supporting weak
boundary-layer instability. As Francine approaches, a corresponding
increase in low-level flow and related effective SRH should support
some threat for tornadoes with any low-topped supercells in outer
rain bands to the east-northeast of the central circulation. Latest
guidance continues to suggest that the better tornado potential over
land will occur in the Day 2/Wednesday time frame (after 12Z). But,
an isolated/marginal tornado threat still remains apparent along
parts of the LA Coast for the last few hours of the Day 1 period
(08-12Z) early Wednesday morning, where a Marginal Risk has been
maintained.

$$

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ACUS01 KWNS 110040
SWODY1
SPC AC 110038

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0738 PM CDT Tue Sep 10 2024

Valid 110100Z - 111200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
COASTAL AND SOUTHEAST LOUISIANA...

...SUMMARY...
Marginal tornado potential may reach coastal areas of Louisiana
during the late overnight/early morning hours.

...01Z Update...
An increasing, but low-probability, tornado threat is still
anticipated tonight into early Wednesday morning over the LA Coast
as rainbands associated with TC Francine move across the area.

Isolated thunderstorms will continue across the central/southern
Rockies and central High Plains for the next several hours before
waning buoyancy and nocturnal stabilization result in diminishing
coverage. Additional thunderstorms are also still expected tonight
through tomorrow morning along the Pacific Northwest coast and into
the northern Rockies as a strong shortwave trough approaches the
Pacific Northwest coast.

..Mosier.. 09/11/2024

$$

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ACUS01 KWNS 110549
SWODY1
SPC AC 110547

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1247 AM CDT Wed Sep 11 2024

Valid 111200Z - 121200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE CENTRAL GULF COAST...

...SUMMARY...
A few tornadoes are possible across the central Gulf Coast vicinity
on Wednesday into Wednesday night, in association with Tropical
Cyclone Francine.

...Central Gulf Coast...
Hurricane Francine is forecast to continue northeastward across the
northwest Gulf of Mexico today, likely making landfall over the
central LA Coast during the afternoon. Easterly/northeasterly winds
are expected across much of the Southeast from the morning through
the afternoon, which will likely keep the tropical airmass
associated with this cyclone offshore (or only over immediate
coastal portions of south-central and southeast LA). As the storm
makes landfall, mid 70s dewpoints will spread northward into more of
southeast LA, southern MS, southern AL, and the far western FL
Panhandle during the evening. This increased low-level moisture
could boast buoyancy enough for more sustained/persistent updrafts.
Robust low to mid-level wind fields associated with the cyclone will
support rotation within any more persistent updrafts, with some
isolated low-topped supercells possible.

Current guidance suggests the highest tornado potential will exist
from 21Z through 04Z from far southeast LA across southern MS/AL.
Mid 70s dewpoints and southerly/southeasterly surface winds will
persist from southern MS/AL into the far western FL Panhandle,
supporting a low-probability tornado risk through early Thursday
morning.

...Parts of the Northwest/Northern Rockies...
The strong shortwave trough currently off the Pacific Northwest
coast is forecast to continue eastward throughout the period, while
also deepening/maturing. By early Thursday morning, this shortwave
trough will likely extend from the ID Chimney/northwest MT into the
Great Basin. Strong mid-level flow will accompany this shortwave,
spreading eastward from northern CA through the Great Basin as the
wave progresses eastward.

Relatively cool mid-level temperatures are already in place from the
northern Intermountain West into the northern Rockies, with 500 mb
temperatures from -11.5 to -14 deg C sampled on the regional 00Z
soundings. Strong heating and boundary-layer mixing beneath these
cool mid-level temperature will result in modest buoyancy during the
afternoon ahead of the shortwave trough. Afternoon thunderstorm
development is anticipated as large-scale ascent increases amid this destabilized and modest buoyant airmass. The stronger flow and
vertical shear will be displaced south of the region, but moderate
shear combined with the cool temperatures aloft could still
contribute to some isolated hail. High cloud bases and resultant
strong outflow could result in some gusty winds as well.

...Northern High Plains...
Lee surface troughing will deepen throughout the day, with
southeasterly surface winds increasing in response. Strong
heating/mixing is anticipated across the region. Low-level moisture
advection may help offset some of this mixing but dewpoints will
likely still drop into the mid 40s to low 50s across much of the
region. Highest dewpoints are anticipated across northeastern MT and
western North Dakota. Even with this limited moisture, the strong
heating should destabilize the airmass. Late afternoon thunderstorms
are anticipated with this destabilized airmass as both increasing
large-scale ascent and low-level convergence provide the lift needed
for convective initiation. Vertical shear will likely be strong
enough for some updraft organization (particularly across northwest
MT), and high cloud bases will contribute to the potential for
strong outflow capable of damaging gusts.

..Mosier/Lyons.. 09/11/2024

$$

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ACUS01 KWNS 111243
SWODY1
SPC AC 111242

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0742 AM CDT Wed Sep 11 2024

Valid 111300Z - 121200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN THE CENTRAL
GULF COAST VICINITY...

...SUMMARY...
Hurricane Francine poses a tornado threat today and tonight in the
central Gulf Coast vicinity.

...Synopsis...
The midlatitude westerly belt will amplify somewhat in mid/upper
levels, related somewhat to general height rises over the mid/upper
Mississippi Valley, Great Lakes and Northeast. However, the main
influence will be troughing related to a cyclone now closing off,
just offshore from the Pacific Northwest Coast. The trough will
move inland today and cross the interior Northwest, reaching an axis
from southern BC across eastern parts of WA/OR to the Sierra south
of RNO by 00Z. By 12Z, the trough should extend from the
southernmost Canadian Rockies, across westernmost MT, through a
500-mb low over eastern ID, to near LAS, with associated cyclonic
flow covering most of the CONUS west of 100W and north of 35N.

Farther southeast, moisture-channel imagery indicates that a weak,
cut-off, 500-mb low analyzed last night at 00Z over north-central TX
has moved little since. However, the low is expected to drift/
redevelop northeastward through the period, reaching southeastern OK
by 12Z tomorrow. In response, and as forecast by NHC, Hurricane
Francine should move inland tonight across southeastern LA, and into southwestern MS before daybreak tomorrow.

At the surface, 11Z analysis showed a quasistationary front from
northern FL across the shelf waters of the FL Panhandle/AL/MS,
becoming a diffuse warm front over the Mississippi River mouth and
southern Terrebonne Parish, then just offshore again around the northern/northwestern rim of Francine's circulation. This boundary
should move slowly northward/inland over the north-central Gulf
Coast through the period, with the decaying center of Francine
likely catching the front inland tonight. Elsewhere, a lee trough,
with several weak lows attached, was drawn over eastern portions of
MT/WY/CO, and should strengthen today amidst peripheral mass
response to the major mid/upper trough moving into the northwestern
CONUS.

...Gulf Coast: Hurricane Francine...
Increasing southwesterly deep shear on the cyclone as a whole is
expected, contributing to greater asymmetry in the overall precip/
convective pattern, with increasing supercell/tornado potential
today northeast through east of center. The threat is expected to
ramp up through the remainder of the morning, from south to north
and west to east along the coast, with the greatest potential still
appearing to be this afternoon into early evening, near and south of
the I-10/I-12 corridor from southeastern LA eastward toward MOB,
then overnight, spreading eastward into some of the western FL
Panhandle.

This should occur as:
1. Destabilization spreads somewhat inland -- both from theta-e
advection along and south of the warm front, and weak diurnal
heating;
2. Relatively large low-level hodographs spread over the region
along and south of the warm front -- in the outer parts of the
closed TC circulation; and
3. Both the greater instability and shear spread into a regime of
developing, discrete to semi-discrete convection in bands that can
organize to supercells.
Overland penetration of the most favorable parameter space will
occur overnight, but should be restricted in extent and magnitude by
abundant inland precip and associated stability, as well as nocturnal/diabatically driven stability inland.

See SPC Mesoscale Discussion 2051 for near-term assessments. Refer
to NHC advisories for forecast track, intensity and tropical watch/
warning information on Francine.

...Northern Rockies to northern High Plains...
Two main regimes are expected to contribute to high-based
thunderstorms, atop well-mixed subcloud layers, with marginal
hail/wind potential (western lobe) and mainly strong/isolated severe
gusts (eastern lobe) in the outlook area, with a relative minimum
but non-zero potential for a severe gust in between.

In the western lobe, scattered afternoon thunderstorms in bands and
clusters should develop as low/middle-level destabilization,
combined with modest but adequate moisture, weakens MLCINH and
strengthens buoyancy. Cooling aloft related to increasing large-
scale lift from DCVA, and in the left-exit region of cyclonically
curved upper-jet segment, will overlie surface heating to steepen
tropospheric lapse rates, with pockets of 250-750 J/kg peak/
preconvective MLCAPE expected to develop. Though north of the
strongest deep shear, the area still will lie under strong difluence
aloft, and 25-35-kt effective-shear magnitudes contributing to some organization.

Farther east over the northern High Plains, marginal low-level
moisture, recycled from the last continental/polar air intrusion,
will keep moisture weak (with post-mixing surface dewpoints in the
40s to low 50s F), yet still just enough to support isolated to
widely scattered thunderstorms this afternoon into early evening.
Activity may be relatively maximized near the intensifying lee
trough, where low-level mass convergence and strong diurnal heating
will combine to eradicate CINH. Deep subcloud layers with steep
lapse rates will support downdraft accelerations, even with modest
updraft buoyancy (MLCAPE generally 500-1000 J/kg). A moist axis
near and parallel to the front will yield higher CAPE, but in a more
strongly capped air mass where initiation and maintenance of
surface-based convection is less certain.

..Edwards/Kerr.. 09/11/2024

$$

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ACUS01 KWNS 111629
SWODY1
SPC AC 111627

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1127 AM CDT Wed Sep 11 2024

Valid 111630Z - 121200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE GULF COAST...

...SUMMARY...
Hurricane Francine will pose a tornado threat through tonight across
the middle Gulf Coast region.

...Gulf Coast - Hurricane Francine...
Hurricane Francine will continue to generally move northeastward
toward the southern Louisiana coast. Reference NHC for the latest
forecast track and intensity details. As Francine approaches the
coast later this afternoon into evening, a considerable
strengthening of east-southeasterly winds on its east-northeast
periphery will lead to an increasing near-shore/inland supercell
risk. This will be in tandem with a northward shift of a maritime
warm front and associated moisture-rich air, which will tend to stay
with about 50-75 miles within the Gulf Coast spanning southeast
Louisiana to the Florida Panhandle. The supercell/tornado risk is
expected to steadily increase this afternoon across southeast
Louisiana, transitioning northeastward toward southeast Mississippi,
southern Alabama and the Florida Panhandle into this evening and
overnight, with a few tornadoes possible regionally.

...Northern Rockies and northern High Plains...
High-based thunderstorms are expected to pose an isolated severe
risk late this afternoon into evening, with severe-caliber wind
gusts a possibility, along with some hail possible as well across
the northern Rockies including parts of Idaho and western Montana.
This is influenced by the lead portion of a Pacific Northwest
upper-level trough, with preceding height falls and the exit region
of the upper jet overspreading the northern Rockies and northern
High Plains through tonight.

Thunderstorms should increase in coverage/intensity by late
afternoon, especially from far southeast Oregon into southern Idaho,
southern Montana and northwest Wyoming. Around 250-750 J/kg MLCAPE
coincident with 25-35 kt of effective shear will support clusters
and bands of storms capable of hail and stronger wind gusts.

Additional widely scattered storms are expected across the northern
High Plains within a modestly moist environment. Dry sub-cloud
layers will support the potential for stronger downdrafts and the
possibility of some severe-caliber wind gusts.

..Guyer/Jirak.. 09/11/2024

$$

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ACUS01 KWNS 111959
SWODY1
SPC AC 111958

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0258 PM CDT Wed Sep 11 2024

Valid 112000Z - 121200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE GULF COAST...

...SUMMARY...
Hurricane Francine will pose a tornado threat through tonight across
the middle Gulf Coast region.

...20z Update...
The forecast remains on track with no changes needed to the current
D1 Outlook. Hurricane Francine continues to move northeastward, with
an increasing threat for tornadoes expected across southern
Louisiana shifting into southeastern Mississippi, southern Alabama,
and the Florida panhandle this evening. See previous discussion
below for more information.

..Thornton/Guyer.. 09/11/2024

.PREV DISCUSSION... /ISSUED 1127 AM CDT Wed Sep 11 2024/

...Gulf Coast - Hurricane Francine...
Hurricane Francine will continue to generally move northeastward
toward the southern Louisiana coast. Reference NHC for the latest
forecast track and intensity details. As Francine approaches the
coast later this afternoon into evening, a considerable
strengthening of east-southeasterly winds on its east-northeast
periphery will lead to an increasing near-shore/inland supercell
risk. This will be in tandem with a northward shift of a maritime
warm front and associated moisture-rich air, which will tend to stay
with about 50-75 miles within the Gulf Coast spanning southeast
Louisiana to the Florida Panhandle. The supercell/tornado risk is
expected to steadily increase this afternoon across southeast
Louisiana, transitioning northeastward toward southeast Mississippi,
southern Alabama and the Florida Panhandle into this evening and
overnight, with a few tornadoes possible regionally.

...Northern Rockies and northern High Plains...
High-based thunderstorms are expected to pose an isolated severe
risk late this afternoon into evening, with severe-caliber wind
gusts a possibility, along with some hail possible as well across
the northern Rockies including parts of Idaho and western Montana.
This is influenced by the lead portion of a Pacific Northwest
upper-level trough, with preceding height falls and the exit region
of the upper jet overspreading the northern Rockies and northern
High Plains through tonight.

Thunderstorms should increase in coverage/intensity by late
afternoon, especially from far southeast Oregon into southern Idaho,
southern Montana and northwest Wyoming. Around 250-750 J/kg MLCAPE
coincident with 25-35 kt of effective shear will support clusters
and bands of storms capable of hail and stronger wind gusts.

Additional widely scattered storms are expected across the northern
High Plains within a modestly moist environment. Dry sub-cloud
layers will support the potential for stronger downdrafts and the
possibility of some severe-caliber wind gusts.

$$

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ACUS01 KWNS 120042
SWODY1
SPC AC 120040

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0740 PM CDT Wed Sep 11 2024

Valid 120100Z - 121200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE CENTRAL GULF COAST IN ASSOCIATION WITH HURRICANE FRANCINE....

...SUMMARY...
Tornado threat continues with Hurricane Francine across the middle
Gulf Coast region.

...01z Update...

Center of Hurricane Francine has moved onshore and will continue
lifting slowly north through sunrise. Stronger, deeper updrafts are
currently located within the eastern hemisphere of the low, per
lightning data, along with a few longer-lived supercells. Have
adjusted severe probabilities down along the western portion of
Francine to reflect the latest position. Tornado threat continues
with stronger supercells.

High-level diffluent flow is noted across the northern Rockies this
evening ahead of a pronounced short-wave trough that currently
extends across eastern WA/OR into NV. 500mb speed max will dig into
the base of the trough later tonight across the Great Basin which
will ensure the left-exit region of the jet will spread across
eastern ID/southern MT/western WY. Considerable amount of lightning
is currently noted with convection ahead of the short wave, and some
stronger wind gusts have also been observed. 00z sounding from Great
Falls, MT exhibited meager buoyancy, but steep lapse rates are
contributing to MLCAPE on the order of 500 J/kg across southern MT
into eastern ID/western WY. This continues to favor some risk for
locally severe winds with the more robust convection this evening.

..Darrow.. 09/12/2024

$$

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ACUS01 KWNS 121249
SWODY1
SPC AC 121248

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0748 AM CDT Thu Sep 12 2024

Valid 121300Z - 131200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE NORTHERN GREAT PLAINS...AND FROM THE FLORIDA PANHANDLE TO
NORTH-CENTRAL ALABAMA...

...SUMMARY...
A few tornadoes are possible today, mainly in the morning and
afternoon from the Florida Panhandle to north-central Alabama.
Scattered large hail and severe gusts (some significant) are
expected across the eastern Montana vicinity during the afternoon to
early evening.

...Synopsis...
Over the CONUS, in mid/upper levels, a highly amplified initial
pattern will become more blocky through the period. A strong
northern-stream trough with an intermittently closed cyclone is
apparent in moisture-channel imagery from the Canadian Rockies
southward over ID to the central Great Basin. The 500-mb low is
forecast to move northeastward across western and northern MT to
near the southwestern corner of SK by the end of the period. By
then, the attached trough will deamplify slightly and become more
positively tilted, extending from the low to central UT. A
baroclinic leaf with strongly difluent flow aloft precedes the
trough in satellite imagery over southeastern ID, western WY and
central MT, with an eastward shift and some reinforcement expected
today as small vorticity maxima pivot northeastward out of the
trough.

Meanwhile, an initially separate, weak 500-mb low now over the Red
River near PRX, and the remnants of Tropical Storm Francine aloft,
are progged to merge over the upper Delta/Mid-South region today
into tonight. The result after 06Z should be a slow-moving
mid/upper-level low over AR, nearly stacked above the weakening
low-level vortex just to the east around MEM. [See NHC advisories
for latest forecast track/intensity guidance on Francine.] An
anticyclone aloft should form later today and expand tonight
northeast of that low, over the Upper Great Lakes region.

At the surface, 11Z analysis showed a warm front across northernmost
FL to the coastal FL Panhandle, then slightly inland over the
western Panhandle, southwestern AL and southeastern MS. This
boundary will move slowly northward/inland today, demarcating the
north rim of mid-70s F surface dewpoints. Meanwhile, a surface low
was drawn over eastern MT west of GDV, with slow-moving cold front south-southwestward across northeastern/central WY. The low and
front will continue slow/intermittent eastward progress today, then
move into the western Dakotas around 22-00Z, then eastward to the
central Dakotas late overnight.

...Northern Great Plains...
Strong-severe thunderstorms are possible this afternoon into
evening, along and behind the front, with the most probable severe
potential arising from activity moving north-northeastward from
northern WY. High-based supercells and multicells are possible,
offering large hail and severe gusts. Some of the activity may
aggregate upscale into one or two bowing clusters, racing northward
accompanied by a swath of better-organized, potentially significant
(65+ kt) gust potential.

Thunderstorms may develop along the front in early-mid afternoon, as
well as in and near the Bighorns, where diurnal heating of elevated
terrain preferentially removes MLCINH earliest. A corridor of
favorable surface moisture will remain near and behind the front and
ahead of this convection. Meanwhile, midlevel temperatures will
cool and steepen low/middle-level lapse rates, as large-scale ascent
spreads over the area, both ahead of the ejecting mid/upper trough
and in the left-exit region of a cyclonically curved 300-mb jet
segment. This will occur atop a deep and well-mixed boundary layer
containing nearly dry-adiabatic lapse rates. A northerly flow
component west of the front will enhance storm-relative winds in the
inflow layer, as well as low-level and deep-layer shear,
strengthening lift and helping to maintain and further organize the
convection. MLCAPE of 500-1200 J/kg and 45-55 kt effective-shear
magnitudes will support the severe potential.

Convection forming later and farther east near the front over the
western Dakotas, from late afternoon into evening, also may pose a
strong to locally severe gust threat for a few hours, and the
marginal outlook area has been expanded eastward somewhat to give
more room for that process. Flow aloft will bear a substantial
component parallel to the convective axis, indicating a largely
training or linear configuration is possible, along the western rim
of a 50-60-kt LLJ fostering warm advection and moisture transport
above the surface. However, the near-surface airmass over the
central Dakotas should stabilize with time and eastward extent
tonight, limiting duration and eastward shift of the threat.

...Southeastern CONUS...
Tropical Storm Francine is forecast to continue moving northward
over MS, and to lose definition as it interacts more closely with
the mid/upper-level low. Accordingly, associated deep-layer winds
will continue to weaken, but low-level shear will remain favorable
through most of the day well east-southeast to southeast of center.
A destabilizing airmass along and south of the warm/marine front
will support a continued, slow inland shift of supercell potential
amid enlarged hodographs. The favorable environment will be bounded
on the west by a dry slot and veering low-level flow, on the
northeast by unsuitably stable air in heavy precip and north of the
front, and on the south by a gradual weakening of low-level winds
and shear as the cyclone center pulls away and fills. In the
favorable corridor, where inflow parcels are surface-based, expect
effective SRH in the 200-500 J/kg range, very rich moisture, low
LCL, and weak MLCINH. The threat should diminish overnight as the
airmass slowly stabilizes inland, and the system continues to weaken
overall.

..Edwards/Kerr.. 09/12/2024

$$

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ACUS01 KWNS 121639
SWODY1
SPC AC 121638

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1138 AM CDT Thu Sep 12 2024

Valid 121630Z - 131200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN
MONTANA AND WESTERN NORTH DAKOTA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
SOUTHEAST...

...SUMMARY...
A few tornadoes are possible today from northern Florida to
north-central Alabama. Scattered large hail and severe wind gusts
(some significant) are expected across eastern Montana into western
North Dakota this afternoon through early/mid-evening.

...Northern Great Plains including eastern MT/western ND...
Have upgraded portions of eastern Montana and western North Dakota
for a heightened/focused potential for severe storms capable of
large hail and potentially significant-caliber severe wind gusts
later this afternoon through around mid-evening.

Strong-severe thunderstorms are expected, along and behind the
front, as early as early/mid-afternoon, with the most probable
severe potential arising from activity moving north-northeastward
from northern Wyoming and far southern Montana. High-based
supercells and multicells are possible, offering large hail and
severe wind gusts. These storms may aggregate and grow upscale into
one or two bowing clusters, racing north-northeastward accompanied
by a swath of better-organized, potentially significant (65+ kt)
gust potential.

This scenario will be supported by trough-related cooling mid-level temperatures and steep low/mid-level rates atop a modestly moist
boundary layer, as the exit region of a strong upper-level jet
overspreads the region. MLCAPE of 500-1200 J/kg and 45-55 kt
effective-shear magnitudes will support the severe potential
including fast-moving and relatively long-lived storms into western
North Dakota. The near-surface airmass over the central Dakotas
should stabilize with time and eastward extent tonight, limiting
duration and eastward shift of the threat.

...Southeast...
Current Tropical Depression Francine is forecast to continue moving
generally northward over Mississippi, and to lose definition as it
interacts more closely with the mid/upper-level low. Associated
deep-layer winds will continue to weaken, but low-level shear will
remain favorable through most of the day, well to the east-southeast
of its center. A destabilizing airmass along and south of the
warm/marine front will support a continued, slow inland shift of
supercell potential amid enlarged hodographs. The favorable
environment will be bounded on the west by a dry slot and veering
low-level flow, on the northeast by more stable air in heavy precip
north of the front, and on the south by a gradual weakening of
low-level winds and shear as the cyclone center pulls away and
fills. In the favorable corridor, where inflow parcels are
surface-based, expect effective SRH in the 200-500 m2/s2 range, very
rich moisture, low LCL, and weak MLCINH. In the shorter term, a
tornado threat may persist this afternoon across northern Florida,
while potentially increasing later this afternoon through early
evening near the warm front across southern into central Alabama.

..Guyer/Jirak.. 09/12/2024

$$

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ACUS01 KWNS 121954
SWODY1
SPC AC 121952

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0252 PM CDT Thu Sep 12 2024

Valid 122000Z - 131200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN
MONTANA AND WESTERN NORTH DAKOTA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
SOUTHEAST...

...SUMMARY...
A few tornadoes are possible today from northern Florida to
north-central Alabama. Scattered large hail and severe wind gusts
(some significant) are expected across eastern Montana into western
North Dakota this afternoon through early/mid-evening.

...20z...
The D1 Convective Outlook remains on track with no updates needed.

A narrow corridor of tornado risk associated with Tropical
Depression Francine and the mid/upper low across the southeast will
continue across central/southern Alabama this afternoon and evening.
See MCD#2061 for more information.

Across the northern Great Plains, potential for significant damaging
winds will increase through the afternoon and evening as ongoing
convection across Montana and Wyoming increases in coverage and tend
to grow upscale through the evening. See previous discussion for
more information on this threat.

..Thornton.. 09/12/2024

.PREV DISCUSSION... /ISSUED 1138 AM CDT Thu Sep 12 2024/

...Northern Great Plains including eastern MT/western ND...
Have upgraded portions of eastern Montana and western North Dakota
for a heightened/focused potential for severe storms capable of
large hail and potentially significant-caliber severe wind gusts
later this afternoon through around mid-evening.

Strong-severe thunderstorms are expected, along and behind the
front, as early as early/mid-afternoon, with the most probable
severe potential arising from activity moving north-northeastward
from northern Wyoming and far southern Montana. High-based
supercells and multicells are possible, offering large hail and
severe wind gusts. These storms may aggregate and grow upscale into
one or two bowing clusters, racing north-northeastward accompanied
by a swath of better-organized, potentially significant (65+ kt)
gust potential.

This scenario will be supported by trough-related cooling mid-level temperatures and steep low/mid-level rates atop a modestly moist
boundary layer, as the exit region of a strong upper-level jet
overspreads the region. MLCAPE of 500-1200 J/kg and 45-55 kt
effective-shear magnitudes will support the severe potential
including fast-moving and relatively long-lived storms into western
North Dakota. The near-surface airmass over the central Dakotas
should stabilize with time and eastward extent tonight, limiting
duration and eastward shift of the threat.

...Southeast...
Current Tropical Depression Francine is forecast to continue moving
generally northward over Mississippi, and to lose definition as it
interacts more closely with the mid/upper-level low. Associated
deep-layer winds will continue to weaken, but low-level shear will
remain favorable through most of the day, well to the east-southeast
of its center. A destabilizing airmass along and south of the
warm/marine front will support a continued, slow inland shift of
supercell potential amid enlarged hodographs. The favorable
environment will be bounded on the west by a dry slot and veering
low-level flow, on the northeast by more stable air in heavy precip
north of the front, and on the south by a gradual weakening of
low-level winds and shear as the cyclone center pulls away and
fills. In the favorable corridor, where inflow parcels are
surface-based, expect effective SRH in the 200-500 m2/s2 range, very
rich moisture, low LCL, and weak MLCINH. In the shorter term, a
tornado threat may persist this afternoon across northern Florida,
while potentially increasing later this afternoon through early
evening near the warm front across southern into central Alabama.

$$

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ACUS01 KWNS 130101
SWODY1
SPC AC 130059

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0759 PM CDT Thu Sep 12 2024

Valid 130100Z - 131200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN HIGH PLAINS...

...SUMMARY...
Severe thunderstorms, associated with severe wind gusts and isolated
large hail, are expected this evening in parts of eastern Montana,
northeast Wyoming and in the western Dakotas. Wind gusts exceeding
70 mph will be possible. Storms with an isolated tornado threat may
also occur this evening in central Alabama.

...Northern High Plains...
At mid-levels, the latest water vapor imagery shows a low in the
northern Rockies, with cyclonic south to southwest flow over the
northern Plains. At the surface, a dual-centered low and an
associated cold front is analyzed across the western Dakotas. Strong
to severe thunderstorms are located near the front, and further west
into the post-frontal airmass in eastern Montana. Within this area
of storms, surface dewpoints are in the 50s F, and the RAP is
currently estimating MLCAPE in the 500 to 1200 J/kg range. Regional
WSR-88D VWPs at Glasgow, Montana and Minot, North Dakota have 0-6 km
shear in the 40 to 50 knot range. In addition, most RAP forecast
soundings near and just behind the front have 700-500 mb lapse rates
between 7.5 and 8 C/km. Surface obs have temperature-dewpoint
depressions mostly varying between 15 and 25 degrees F. This
environment should continue to support supercells with potential for
severe wind gusts. A few gusts over 70 mph will be possible.
Isolated large hail may also occur. The greatest severe threat
should be over far northeastern Montana into far western North
Dakota, near the location of the strongest instability. The threat
should persist through the mid to late evening.

...Central Gulf Coast States...
The latest mosaic radar imagery shows the remnants of post-tropical
cyclone Francine extending from the mid Mississippi Valley
southeastward in the central Gulf Coast states. A band of
thunderstorms is ongoing across northern and central Alabama, where
the RAP is analyzing an axis of instability. Near the axis, the 00Z
sounding at Birmingham has MUCAPE around 600 J/kg, with 0-1 Km shear
near 40 knots. This should support an isolated threat for supercells
and tornadoes. The threat will be concentrated in a relatively small
area across central Alabama, where the combination of instability
and low-level shear is maximized. The threat is expected to be
isolated, and may persist into the late evening.

..Broyles.. 09/13/2024

$$

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ACUS01 KWNS 130535
SWODY1
SPC AC 130533

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1233 AM CDT Fri Sep 13 2024

Valid 131200Z - 141200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHEAST...

...SUMMARY...
An isolated tornado threat is expected to develop this morning and
afternoon across parts of Alabama, western Georgia and middle
Tennessee. A few isolated severe gusts will be possible in parts of
Alabama, southwest Georgia and the Florida Panhandle.

...Southeast...
The remnants of post-tropical cyclone Francine are expected to move
slowly across the lower to mid Mississippi Valley today. To the
southeast of the upper low, an axis of instability is forecast to be
in place across eastern Alabama this morning. As surface
temperatures warm, thunderstorm development be likely along and near
the instability axis. Storms will move northward across eastern
Alabama and middle Tennessee, along and near a corridor of maximized
low-level winds. RAP forecast soundings this morning near this
corridor have 0-1 km shear near 20 knots in northeast Alabama and
around 25 knots in middle Tennessee. This suggests a low-end
potential for tornadoes associated with semi-discrete rotating
cells. The threat may continue into the afternoon as instability
maximizes across the region. A potential for severe gusts will also
be possible across Alabama extending southward into the Florida
Panhandle, where low-level shear may not be as strong but moderate
instability is expected to develop.

..Broyles/Weinman.. 09/13/2024

$$

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ACUS01 KWNS 131245
SWODY1
SPC AC 131243

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0743 AM CDT Fri Sep 13 2024

Valid 131300Z - 141200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM MIDDLE
TENNESSEE TO THE FLORIDA PANHANDLE...

...SUMMARY...
A marginal tornado threat is expected to develop this morning and
afternoon across parts of Alabama, western Georgia and middle
Tennessee. Isolated damaging to severe gusts will be possible in
parts of Alabama, southwest Georgia and the Florida Panhandle.

...Synopsis...
In mid/upper levels, the CONUS portion of the large-scale pattern
this period will be characterized by a "dirty" Rex block in the
East, and troughing in the West. The block will be composed of an
anticyclone drifting eastward over the Upper Great Lakes, and a
small, deep-layer cyclone -- resulting from the merger of a weak,
midlatitude, mid/upper-tropospheric low with the low/middle-level
remnants of post-tropical cyclone Francine -- centered currently
near BVX. This low should weaken gradually and meander slowly over
the Mid-South, possibly drifting east-southeastward back across the
MEM area through the period, but with negligible movement on the
synoptic scale.

In the northern stream, a mid/upper-level cyclone -- evident in moisture-channel imagery over southern SK -- will eject
northeastward to northern MB and devolve to an open-wave trough by
12Z tomorrow. In its wake, broadly cyclonic flow aloft, with mostly
minor embedded shortwaves/vorticity maxima -- will cover the
northwestern 1/4 of the CONUS. To its east, midlevel DCVA/ascent
from a weak trough trailing the cyclone, combined with low-level
warm advection and gradual moistening, will support general thunder
potential over portions of the northern Plains to upper Mississippi
Valley.

At the surface, 11Z analysis showed a wavy, quasistationary to warm
front extending from off the SC Coast across southern GA and
eastern/northern AL, intersecting a weak cold front there, then as
an occluded front into the low over AR. This boundary should drift
diffusely northward through the period, while weakening. A
stationary to slow cold front was drawn from southern MB across
central ND and western SD, and should drift eastward over the
central Dakotas today through tonight.

...Southeast...
Isolated, mostly short-lived supercells will be possible today,
mainly in a belt of low-level convergence from parts of central/
eastern AL and western GA into the Tennessee Valley, with a marginal
tornado threat. Farther south, in weaker shear (but greater
instability), a few of the stronger cells or small clusters may
produce damaging gusts.

A corridor of relatively maximized low-level shear/SRH remains near
the old, diffuse warm-frontal zone well southeast of the center of
Francine's remnants. Both that and a moisture/buoyancy axis to its
west (centered roughly over the axis of the outlooked corridor)
should move little today, given the slow filling and lack of motion
of the related deep-layer cyclone over the Mid-South. Rich low-
level moisture will persist in this corridor, with surface dewpoints
commonly in the 70s F, and low LCLs. Weaknesses of both surface
winds and midlevel flow will sandwich a 35-40-kt east-southeasterly
to southeasterly LLJ that keeps hodographs somewhat enlarged and
effective SRH in the 150-300 J/kg range over eastern/northern AL
into southern mid TN. With some localized help from boundaries
(outflow or differential-heating), a brief tornado is possible. A
few of the most vigorous, water-loaded downdrafts will be capable of
localized strong to marginally severe gusts, especially over
southern areas where peak MLCAPE may reach about 2000 J/kg.
Activity generally should weaken this evening and overnight as the
airmass stabilizes and the remnants of Francine continue to decay.

..Edwards/Mosier.. 09/13/2024

$$

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ACUS01 KWNS 131630
SWODY1
SPC AC 131628

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1128 AM CDT Fri Sep 13 2024

Valid 131630Z - 141200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHEAST...

...SUMMARY...
A marginal/isolated tornado threat should continue through this
afternoon across parts of Alabama, western Georgia, and middle
Tennessee. Isolated damaging winds may also occur.

...Southeast...
The remnant surface circulation associated with Francine located
over AR late this morning is forecast to continue filling/weakening
through the day as a weak mid-level trough across the Mid-South
moves slowly eastward. Surface observations/analysis indicate a
front is draped northwest to southeast from western TN into
northern/central AL and southern GA. This boundary may serve as a
focus for additional convective development this afternoon, even
though the overall system is weakening. Cloud cover remains
prevalent across much of this region, which should hinder daytime
heating to some extent. Poor mid-level lapse rates are also present,
which will likely limit updraft intensities. Even with a marginal
thermodynamic environment expected, modest but sufficient low-level
shear will persist through at least early afternoon. This may
support occasional low-level updraft rotation, and the threat for a
tornado or two. Otherwise, occasional damaging winds may also occur
with any robust thunderstorm that can persist. This
isolated/marginal severe threat should remain focused along/near the
surface front, before waning this evening with the loss of daytime
heating.

..Gleason/Leitman.. 09/13/2024

$$

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ACUS01 KWNS 131947
SWODY1
SPC AC 131945

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0245 PM CDT Fri Sep 13 2024

Valid 132000Z - 141200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHEAST...

...SUMMARY...
A marginal/isolated tornado threat should continue through this
afternoon across parts of Alabama, western Georgia, and middle
Tennessee. Isolated damaging winds may also occur.

...20z Update...
No changes are needed to the current D1 Convective Outlook. See
previous discussion below for more information.

..Thornton/Gleason.. 09/13/2024

.PREV DISCUSSION... /ISSUED 1128 AM CDT Fri Sep 13 2024/

...Southeast...
The remnant surface circulation associated with Francine located
over AR late this morning is forecast to continue filling/weakening
through the day as a weak mid-level trough across the Mid-South
moves slowly eastward. Surface observations/analysis indicate a
front is draped northwest to southeast from western TN into
northern/central AL and southern GA. This boundary may serve as a
focus for additional convective development this afternoon, even
though the overall system is weakening. Cloud cover remains
prevalent across much of this region, which should hinder daytime
heating to some extent. Poor mid-level lapse rates are also present,
which will likely limit updraft intensities. Even with a marginal
thermodynamic environment expected, modest but sufficient low-level
shear will persist through at least early afternoon. This may
support occasional low-level updraft rotation, and the threat for a
tornado or two. Otherwise, occasional damaging winds may also occur
with any robust thunderstorm that can persist. This
isolated/marginal severe threat should remain focused along/near the
surface front, before waning this evening with the loss of daytime
heating.

$$

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ACUS01 KWNS 140058
SWODY1
SPC AC 140056

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0756 PM CDT Fri Sep 13 2024

Valid 140100Z - 141200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
CENTRAL AND NORTHERN ALABAMA...

...SUMMARY...
Thunderstorms capable of isolated severe gust and a brief tornado
will be possible this evening across parts of central and northern
Alabama.

...Central and Northern Alabama...
The latest water vapor imagery shows a mid-level low over the mid
Mississippi Valley. At the surface, a corridor of maximized
low-level moisture is located from Alabama into Tennessee, where the
RAP is analyzing MLCAPE in the 1000 to 1500 J/kg range. Scattered
thunderstorms are ongoing from south-central Alabama
north-northwestward into Tennessee. The Birmingham 00Z sounding is
located near the instability axis, and has a low-end supercell wind
profile with 0-6 km shear in the 35 to 40 knot range. This could
support an isolated threat for severe gusts over the next couple of
hours. A brief tornado could also occur. However, low-level lapse
rates are poor and low-level shear is weak. As the boundary layer
cools, the environment should become less favorable for severe
storms.

..Broyles.. 09/14/2024

$$

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ACUS01 KWNS 140543
SWODY1
SPC AC 140541

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1241 AM CDT Sat Sep 14 2024

Valid 141200Z - 151200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
NORTHERN NEBRASKA AND WEST-CENTRAL SOUTH DAKOTA...

...SUMMARY...
Thunderstorms capable of isolated severe gusts and hail will be
possible in parts of northern Nebraska and west-central South
Dakota.

...Northern Nebraska/West-central South Dakota...
A shortwave trough will move northeastward across the northern and
central High Plains today. At the surface, a trough will develop in
the northern High Plains, with the western edge of a moist airmass
located in the western Dakotas. As surface temperatures warm today
within this airmass, a narrow corridor of moderate instability is
expected to develop from northwestern Nebraska into western South
Dakota. Thunderstorms will be possible near and to the east of this
axis of instability during the afternoon. RAP forecast soundings at
21Z at Pierre, South Dakota have MLCAPE near 800 J/kg, with 0-3 km
lapse rates between 8.5 and 9 C/km, and 0-6 km shear around 30
knots. This should be enough for a marginal severe threat near peak
heating. The strongest of cells could produce isolated severe wind
gusts and hail.

..Broyles/Weinman.. 09/14/2024

$$

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ACUS01 KWNS 141244
SWODY1
SPC AC 141242

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0742 AM CDT Sat Sep 14 2024

Valid 141300Z - 151200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
THE NORTH-CENTRAL PLAINS...

...SUMMARY...
Thunderstorms capable of isolated severe gusts and hail will be
possible over parts of the north-central Plains.

...Synopsis...
Blockiness in the eastern CONUS will continue to dominate the
large-scale, mid/upper-level pattern through the period. An
anticyclone will drift eastward to southeastward over the Great
Lakes, poleward of a broad belt of low heights and several embedded
vorticity maxima extending from the lower Mississippi Valley to
offshore from the Carolinas. One of those perturbations will be the
decaying remnants of a merger of a midlatitude mid/upper low with
the remnants of Francine. This feature is forecast to drift
erratically eastward to southeastward over the Mid-South,
contributing to convective potential over a broad area of the
Southeast, but with wind fields and lift too weak to support
organized severe potential.

Farther west, synoptic-scale height rises are forecast across most
of the central/northern Plains, as a strong trough digs south-
southeastward near the BC Coast and forms a 500-mb low near UIL at
the end of the period. By then, associated cyclonic flow should
cover a large part of the CONUS west of the Rockies, as well as for
several hundred miles off the West Coast.

The 11Z surface analysis showed a low over northern MS (associated
with the remnants of Francine) with an occluded front arching across
AL to a triple point near MGM, a warm front across southern GA, and
a cold front across the western FL Panhandle. These boundaries
should become more diffuse with time today as the deep-layer cyclone
above the low continues its gradual degradation. Meanwhile, a
quasistationary front from east-central ND across central SD to
southwestern NE should weaken through the day, but with a remnant trough/convergence zone lingering near the present position. A weak
surface low should form farther west today, in northeastern WY east
of GCC, then migrate eastward into western SD toward RAP tonight.

...North-central Plains...
Isolated to scattered thunderstorms are expected to develop this
afternoon, in a narrow corridor of relatively maximized low-level
convergence (corresponding to the weak front/trough) and favorably
strong surface heating east through southeast of the low. Isolated
severe gusts and hail will be possible as convection proceeds across
SD and perhaps into southern ND this evening, before encountering
progressively more-stable low-level conditions with a decreasing
severe threat. A weak perturbation apparent in moisture-channel
imagery over east-central WY should move northeastward across the
western NE Panhandle to southwestern/south-central SD by mid/late
afternoon, and may contribute subtle large-scale ascent to the
environment. Still, with broader, ambient height rises superimposed
on that, considerable mesoscale timing/location uncertainty remains
on the most probable initiation zone within the southern part of the
outlook area. The later initiation occurs, the farther north the
unconditional severe-threat area will be.

Activity should move north-northeastward into a corridor of
favorable moisture and buoyancy, with peak MLCAPE in the 500-1500
J/kg range, atop a well-mixed subcloud layer. Greater lift and more
backing of low level flow will be present over the SD part of the
outlook, spreading northward into southern ND with time this
evening, and supporting conditional potential for upscale growth of
activity initiating in a hotter boundary layer near the Badlands.
Stronger capping and weaker convergence over western NE cast some
doubt as to formation and convective coverage in the Sandhills,
though the environment will be favorable for marginal severe there
as well. Modest low/middle-level winds nonetheless will veer
strongly with height, leading to 25-35-kt effective-shear magnitudes
in support of some organization.

..Edwards/Mosier.. 09/14/2024

$$

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ACUS01 KWNS 141630
SWODY1
SPC AC 141628

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1128 AM CDT Sat Sep 14 2024

Valid 141630Z - 151200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN/CENTRAL PLAINS...

...SUMMARY...
Thunderstorms capable of producing isolated severe gusts and hail
will be possible over parts of the north-central Plains this
afternoon and evening.

...Northern/Central Plains...
Modest ascent associated with a weak shortwave trough over eastern
WY is encouraging towering cu and recent thunderstorm initiation
across parts of western/central NE late this morning. This
convective development is also occurring along/near a weak surface
trough. Even though large-scale ascent is expected to remain fairly
modest across much of the northern/central Plains today in the wake
of a more prominent upper trough moving northeastward over central
Canada, most guidance still shows potential for isolated to
scattered thunderstorms developing this afternoon across parts of
northwest NE into western/central SD along/near the surface trough.
With modest/shallow low-level moisture in place, but steep mid-level
lapse rates per 12Z LBF/UNR soundings, robust daytime heating will
likely support around 1000-2000 J/kg of MLCAPE by mid afternoon.

West-southwesterly flow at mid levels is forecast to be only
modestly enhanced by the passing shortwave trough. Still, a veering
and gradually strengthening wind profile with height through mid
levels should support around 25-35 kt of deep-layer shear.
Occasional hail may occur with any marginal supercells that can
initially develop, although tendency for clustering and outflow
interactions may lead to an isolated severe wind threat with time
late this afternoon and early evening. The overall severe risk
should quickly wane this evening with the loss of daytime heating.

...Southern High Plains...
At least isolated high-based thunderstorms should develop this
afternoon across parts of the TX Panhandle and vicinity along/east
of a weak surface front/trough. With a deeply mixed boundary layer
expected with daytime heating, occasional strong/gusty downdraft
winds may occur with the more robust cores. However, weak deep-layer
shear should keep the overall severe wind threat rather isolated.

...East Texas into Southern Louisiana/Mississippi...
Isolated to widely scattered thunderstorms may develop along a weak
front from parts of east TX into southern LA/MS later this
afternoon. This activity would occur on the back side of a remnant
mid-level circulation over the Mid-South. While modestly enhanced
mid-level flow will be present, the potential for a more organized
severe wind threat appears too low to include probabilities at this
time.

..Gleason/Dean.. 09/14/2024

$$

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ACUS01 KWNS 141954
SWODY1
SPC AC 141952

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0252 PM CDT Sat Sep 14 2024

Valid 142000Z - 151200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN/CENTRAL PLAINS...

...SUMMARY...
Thunderstorms capable of producing isolated severe gusts and hail
will be possible over parts of the north-central Plains this
afternoon and evening.

...20z Update...
Minimal changes have been made to trim the northern Plains Marginal
behind ongoing convection, otherwise the Day 1 Convective Outlook
remains on track. See previous discussion below for more
information.

..Thornton/Gleason.. 09/14/2024

.PREV DISCUSSION... /ISSUED 1128 AM CDT Sat Sep 14 2024/

...Northern/Central Plains...
Modest ascent associated with a weak shortwave trough over eastern
WY is encouraging towering cu and recent thunderstorm initiation
across parts of western/central NE late this morning. This
convective development is also occurring along/near a weak surface
trough. Even though large-scale ascent is expected to remain fairly
modest across much of the northern/central Plains today in the wake
of a more prominent upper trough moving northeastward over central
Canada, most guidance still shows potential for isolated to
scattered thunderstorms developing this afternoon across parts of
northwest NE into western/central SD along/near the surface trough.
With modest/shallow low-level moisture in place, but steep mid-level
lapse rates per 12Z LBF/UNR soundings, robust daytime heating will
likely support around 1000-2000 J/kg of MLCAPE by mid afternoon.

West-southwesterly flow at mid levels is forecast to be only
modestly enhanced by the passing shortwave trough. Still, a veering
and gradually strengthening wind profile with height through mid
levels should support around 25-35 kt of deep-layer shear.
Occasional hail may occur with any marginal supercells that can
initially develop, although tendency for clustering and outflow
interactions may lead to an isolated severe wind threat with time
late this afternoon and early evening. The overall severe risk
should quickly wane this evening with the loss of daytime heating.

...Southern High Plains...
At least isolated high-based thunderstorms should develop this
afternoon across parts of the TX Panhandle and vicinity along/east
of a weak surface front/trough. With a deeply mixed boundary layer
expected with daytime heating, occasional strong/gusty downdraft
winds may occur with the more robust cores. However, weak deep-layer
shear should keep the overall severe wind threat rather isolated.

...East Texas into Southern Louisiana/Mississippi...
Isolated to widely scattered thunderstorms may develop along a weak
front from parts of east TX into southern LA/MS later this
afternoon. This activity would occur on the back side of a remnant
mid-level circulation over the Mid-South. While modestly enhanced
mid-level flow will be present, the potential for a more organized
severe wind threat appears too low to include probabilities at this
time.

$$

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ACUS01 KWNS 150055
SWODY1
SPC AC 150054

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0754 PM CDT Sat Sep 14 2024

Valid 150100Z - 151200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL AND NORTHERN PLAINS...

...SUMMARY...
Thunderstorms capable of producing isolated severe gusts and hail
will be possible this evening over parts of the central and northern
Plains.

...Central and Northern Plains...
The latest water vapor imagery shows a shortwave trough over the
Dakotas extending southward into northern Nebraska. Along this
corridor, the RAP has a two distinct vorticity maxima analyzed. At
the surface, a trough is located in the northern High Plains, and a
moist airmass is present over much of the central and northern
Plains. Surface dewpoints within this moist airmass vary from the
mid 50s to mid 60s F. The RAP suggests that moderate instability is
present from west-central Nebraska into parts of the Dakotas, where
isolated to scattered thunderstorms are ongoing. The North Platte
00Z sounding has the best severe environment regionally, with MLCAPE
near 1500 J/kg, and 0-3 km shear around 35 knots. On this sounding,
the average low to mid-level lapse rate is near 7.5 C/km. This,
along with instability and shear suggest that a marginal severe
threat will likely continue for a few more hours. Isolated severe
gusts and hail will be possible with rotating cells. The threat is
expected to diminish during the mid to late evening as instability
decreases across the region.

..Broyles.. 09/15/2024

$$

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ACUS01 KWNS 150559
SWODY1
SPC AC 150558

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1258 AM CDT Sun Sep 15 2024

Valid 151200Z - 161200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL AND NORTHERN HIGH PLAINS...

...SUMMARY...
Thunderstorms capable of isolated severe gusts and hail will be
possible today across parts of the central and northern High Plains.

...Central and Northern High Plains...
An upper-level low will move southward along the West Coast today,
as southwest mid-level flow remains over much of the western third
of the U.S. A subtle shortwave trough is forecast to move
northeastward through the central Rockies. Ahead of the trough, a
moist airmass will be in place in the central and northern Plains,
where surface dewpoints will mostly be from the upper 50s to the mid
60s F. As surface temperatures warm, moderate instability is
expected to develop over much of this airmass. MLCAPE is forecast to
peak in the 2000 to 3000 J/kg range in areas that heat up the most.
The instability axis is forecast to be located from northwest Kansas
northward into western Nebraska and southwest South Dakota by mid to
late afternoon. At this time, RAP forecast soundings near the
instability axis have low to mid-level lapse rates exceeding 8 C/km,
and enough deep-layer shear for a marginal severe threat. Isolated
severe gusts and hail will be possible with the stronger cells,
mainly during the late afternoon and early evening.

..Broyles/Weinman.. 09/15/2024

$$

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ACUS01 KWNS 151252
SWODY1
SPC AC 151250

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0750 AM CDT Sun Sep 15 2024

Valid 151300Z - 161200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL AND NORTHERN HIGH PLAINS...

...SUMMARY...
Thunderstorms capable of isolated severe gusts and hail will be
possible today across parts of the central and northern High Plains.

...Synopsis...
In mid/upper levels, a blocky longwave pattern will remain over the
CONUS, with amplifying troughing in the West and a Rex configuration
in the East. Cyclonic flow already covers most of the land west of
the Rockies. That will continue but with backing of the flow aloft,
as a cyclone now centered over Vancouver Island strengthens and digs south-southeastward down the West Coast. By 12Z tomorrow, the
associated 500-mb low should be located near OAK, with strongly
difluent flow and modest ridging over the High Plains from eastern
NM to MT. The southern part of a weak shortwave trough -- evident
in moisture-channel imagery from UT to eastern AZ -- should cross CO
today and reach the eastern border of WY to near GLD by 12Z, likely
enhanced from this evening onward by convectively generated
vorticity.

A mid/upper anticyclone now over the Lower Great Lakes will stretch
eastward and open up to that direction around the end of the period.
The base of the eastern pattern block will be composed of a broad,
nearly zonal height weakness anchored by:
1. The decaying remains of Francine, long merged with a mid/upper
low, and forecast to drift erratically over the Mid-South while
weakening further;
2. An intensifying, deep-layer cyclone with low-level manifestation
as a deepening wave cyclone along a frontal zone, offshore from the
Carolinas.

The 11Z surface analysis showed a wavy, quasistationary frontal zone
attached to a strengthening low located roughly south of EWN and
east of SAV. The front extended across northern FL to the western
FL Panhandle and southwestern AL. A remnant low was drawn well
inland over northern MS, connecting to the Gulf boundary via an
occluded front. These features should move little through the
period, but with further weakening of the western low, and
intensification of the eastern one. Elsewhere, a lee trough and
dryline either overlapped, or were drawn within less than 100 nm
apart, near the eastern border of WY, eastern CO, the northern/
western TX Panhandle, and east-central/southeastern NM. The dryline
should shift somewhat eastward today amid diurnal heating.

...Central/northern High Plains...
Isolated to widely scattered thunderstorms are possible across a
large part of the Rockies, Intermountain West, and Desert Southwest
today. Some of this activity will mature atop deep, well-mixed
boundary layers of desert valleys and the High Plains, with non-zero
potential for a strong-severe gust. The most concentrated/organized
potential for gusts near to above severe limits, as well as marginal
hail, still appears to be over portions of the central High Plains
into the Black Hills and vicinity, near the lee trough/dryline.
East of that, low-level moisture will be relatively maximized in a
return-flow airmass of predominantly continental origin, with a
north-south belt of 50s to mid 60s F surface dewpoints. Where the
western part of that moisture coincides with strong surface heating,
and underlies the eastern part of the EML, a north-south corridor of
MLCAPE in the 1500-2500 J/kg range should develop, with 500-1500
J/kg extending into the more deeply mixed regime nearest the lee
trough. East of the trough, considerable veering of winds with
height is expected, with some low-level hodograph enhancement
potentially moving 0-3-km SRH to near 150 J/kg, but lack of stronger
midlevel flow will temper overall shear.

...Coastal NC, extreme eastern SC...
Many progs deepen the low-level cyclone and transition it to
subtropical or tropical character through the end of day 2, while
eroding the frontal zone's baroclinicity; however, inconsistency
among models is high. The most aggressive among the synoptic and
CAM guidance with the speed of the transition and approach to the
coast (e.g., 06Z GFS and 00Z ARW high-res window respectively) show
favorably large low-level shear, but barely have surface-based
effective inflow onshore at the end of the period, with greatest
convective coverage and buoyancy still offshore. As such, the
associated coastal tornado threat still appears too low and
conditional to outlook until day 2 (after 16/12Z). Potential for
faster/deeper development and shoreward translation of the low will
continue to be monitored for onshore supercell threat the last few
hours of day 1. See latest NHC tropical outlook for guidance on
overall development potential with this system.

..Edwards/Mosier.. 09/15/2024

$$

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