AWUS01 KWNH 120901
FFGMPD
ALZ000-MSZ000-LAZ000-ARZ000-121500-

Mesoscale Precipitation Discussion 0993
NWS Weather Prediction Center College Park MD
500 AM EDT Thu Sep 12 2024

Areas affected...Much of MS...Western AL

Concerning...Heavy rainfall...Flash flooding possible

Valid 120900Z - 121500Z

SUMMARY...Moderate to heavy rain associated with weakening
Tropical Storm Francine will continue to foster a threat for areas
of flash flooding going through the morning hours.

DISCUSSION...Tropical Storm Francine at 09Z (4AM CDT) is located
60 miles north of New Orleans, LA and is moving northeast at 12
mph. The storm continues to rapidly weaken as it moves farther
inland, and the latest radar and satellite data suggests Francine
is rather quickly acquiring extratropical characteristics as the
storm merges with a frontal zone and an approaching upper-level
trough to its west over the lower MS Valley.

Francine currently has a distinct lack of convection near the
center, with much of the heavy rainfall now north of the center
over central MS, and also in several convective bands well east of
the center involving southwest AL and the western FL Panhandle.
The rainfall over much of central MS is being driven by strong
warm air advection/isentropic ascent given interaction with the
aforementioned frontal zone. A southerly low-level jet of 40 to 60
kts is seen advancing north around the eastern quadrant of
Francine's circulation, and this is a key player in driving
enhanced low-level forcing and moisture transport.

Much of the stronger instability is becoming detached from
Francine's center of circulation, and this has been allowing for
the rainfall rates to come down rather substantially over the last
few hours. However, going through the morning hours, the level of frontogenetical forcing, moisture transport and interaction with
the aforementioned upper-level trough should still yield areas of
heavy rainfall with rates that may still occasionally reach 1 to
1.5 inches/hour.

The 00Z HREF guidance suggests additional rainfall amounts going
through 15Z (10AM CDT) of 2 to 4 inches, with isolated heavier
amounts. The antecedent conditions across especially areas of
central and northern MS and western AL are quite dry, so these
rains will initially be going into moistening the soil conditions.
However, given the localized persistence of heavier rainfall rates
and urban sensitivities, some runoff problems and areas of flash
flooding will be possible this morning.

Orrison

ATTN...WFO...BMX...JAN...MEG...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 34139023 34138949 33908861 33318800 32698774
31998780 31548820 31308908 31459011 32119101
33119123 33839095
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