• Heavy Rain/Flood Plains

    From Dumas Walker@21:1/175 to All on Mon Sep 16 08:38:00 2024
    AWUS01 KWNH 161214
    FFGMPD
    KSZ000-NEZ000-SDZ000-161700-

    Mesoscale Precipitation Discussion 1021
    NWS Weather Prediction Center College Park MD
    814 AM EDT Mon Sep 16 2024

    Areas affected...Southeast SD...Central NEB...North-central KS...

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

    Valid 161215Z - 161700Z

    SUMMARY...Persistent, stationary elevated thunderstorms continue
    to produce solid rain-rates that localized totals are nearing
    higher localized FFG values; suggesting flash flooding may become
    possible over the next few hours.

    DISCUSSION...GOES-E WV depicts stronger northern stream shortwave
    and resultant MCS across the Northern Plains; a more subtle wave
    is lifting northeastward along its southern flank across the
    Nebraska Panhandle. This is enhancing low level flow across the
    central Plains with backed 850mb veering through 700mb at 45kts
    reducing to 20kts while also becoming confluent along and just
    east of 99W. CIRA LPW and RAP TPW, show greatest ascent pattern
    is just along the western gradient of the moisture axis with
    1.25-1.5" values noted along it from SE SD into the northern KS
    where deep layer (mainly directional) convergence is maximized.
    MUCAPE appears to be sufficient at 500-1000 J/kg with axis of
    greatest values along and west of the moisture axis, ideally
    supporting the stronger convective ascent. This appears to be
    exhausting as the updrafts/overshooting tops are becoming a bit
    less in coverage and noting a generally slow warming with the
    cirrus canopies associated with the two linear clusters from SE
    SDak into N NEB and again along the NEB/KS line to Lincoln county,
    KS.

    The concern has been/continues to be the relative zero or very
    slight westward propagation of the lines allowing for localized
    enhanced rainfall totals. With deep layer steering more north;
    the inflow from the 850-700mb isentropic ascent/instability axis
    has been nearly equal/opposite to allow for the 1.5-2"/hr rates to
    overcome the regionally above normal FFG values (given the
    prolonged dry period across the region) which are about 3+"/3hrs.
    As such, localized observed totals (per backyard wx stations) are
    reaching 2-3" in spots, and MRMS Flash response are reaching
    300-400 cfs/smi suggesting enhanced flows may be reaching near
    levels typical of localized flash flooding concerns. Given
    overall trends are slowly downward, an additional hour or two will
    become more likely to exceed even these higher FFGs resulting in
    localized possible flash flooding conditions.

    Gallina

    ATTN...WFO...FSD...GID...ICT...LBF...OAX...TOP...

    ATTN...RFC...ABRFC...MBRFC...NWC...

    LAT...LON 44269842 44089772 42799758 40029761 38909767
    38569827 38689867 39079892 39909900 41439917
    42669922 43359916 43749895
    --- SBBSecho 3.20-Linux
    * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175)