• MESO: Heavy rain - AR/MO

    From Weather Alert@454:1/105 to All on Sat Sep 3 09:30:00 2022
    AWUS01 KWNH 030938
    FFGMPD
    MOZ000-ARZ000-031535-

    Mesoscale Precipitation Discussion 0926
    NWS Weather Prediction Center College Park MD
    537 AM EDT Sat Sep 03 2022

    Areas affected...Northeastern AR...Southeastern MO

    Concerning...Heavy rainfall...Flash flooding likely

    Valid 030935Z - 031535Z

    Summary...Training showers and thunderstorms with 1-2"+/hr
    rainfall rates will likely support localized streaks of 2-3"+
    accumulations, isolated to widely scattered instances of flash
    flooding.

    Discussion...Convection has been gradually organizing and
    strengthening this morning near the base of a stalling shortwave trough/upper-level low along the MO/AR border region. As this
    synoptic scale feature becomes wedged between two large scale
    ridges situated over both the western CONUS and Eastern Seaboard,
    a mesoscale region of persistent low-level moisture
    transport/convergence seems to be developing near the base of the aforementioned trough (spcifically over portions of northeastern
    AR and southeastern MO). The environment in this area is currently characterized by 500-1000 J/kg of MU CAPE, precipitable water
    values of 1.8-2.0 inches (near or above the 90th percentile per
    LZK sounding climatology), and effective bulk shear of 20-25 kts.
    This anomalously moist air mass is supporting rainfall rates of
    1-2"+/hr in the heaviest showers and thunderstorms, as SW to NE
    training near the border region is allowing for localized 2"/hr
    exceedance.

    Hi-res model guidance from overnight suggests that the threat for
    localized training of heavy showers and thunderstorms will persist
    for much of the morning across portions of northeastern AR and
    southeastern MO. 00z HREF 2" neighborhood exceedance probabilities
    (over 3-hr) are as high as 40-60%, with more recent HRRR runs also
    consistently depicting streaky localized totals of 2-3"+ (though
    15z). With the expectation for 1-2"+/hr rainfall rates to
    continue, much of the expected rainfall will occur in as little as
    1-2 hours. As 1-3 hr flash flood guidance locally is as low
    1.5-2.0", isolated to widely scattered instances of flash flooding
    are considered likely.

    Churchill

    ATTN...WFO...LSX...LZK...MEG...PAH...SGF...

    ATTN...RFC...ABRFC...LMRFC...MBRFC...NCRFC...NWC...

    LAT...LON 37649053 37258991 36668986 36079009 35649043
    35139121 35089241 35749242 36439189 36719176
    37149195 37569163

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