• MESO: Mesoscale Discussion 0684

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wed May 19 08:32:52 2021
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    ACUS11 KWNS 190832
    SPC MCD 190832=20

    Mesoscale Discussion 0684
    NWS Storm Prediction Center Norman OK
    0332 AM CDT Wed May 19 2021

    Areas affected...portions of south Texas

    Concerning...Severe potential...Watch possible=20

    Valid 190832Z - 191030Z

    Probability of Watch Issuance...40 percent

    SUMMARY...Thunderstorms may develop east of the Rio Grande early
    this morning, bringing a threat for damaging gusts and hail.

    DISCUSSION...At 08z, an outflow boundary stretched westward from
    just north of Corpus Christi to just north of Laredo. South of this
    boundary, surface dewpoints are generally in the low to mid 70s F
    beneath very steep midlevel lapse rates (per 06z BRO RAOB). This is contributing to strong instability, with MLCAPE values greater than
    2500 J/kg present. A thunderstorm cluster has been developing near
    the higher terrain across the Rio Grande in Mexico. This activity
    will gradually spread east over the few several hours.=20

    While effective shear is somewhat marginal across south Texas, a
    modest southerly low level jet coupled with strong instability
    should be sufficient for some organized cluster to track along/east
    of the Rio Grande this morning. Some CAMs depict an organized bow
    moving across this area, though timing of this feature remains
    somewhat uncertain as current convection is developing earlier than
    what has been indicated in forecast guidance. Should an organized
    cluster emerge, damaging gusts (and perhaps hail with any
    semi-discrete cells given very steep midlevel lapse rates) will be
    possible through the morning hours. Convective trends will be
    monitored and a severe thunderstorm watch may be needed in the next
    couple of hours.

    ..Leitman/Hart.. 05/19/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!raiXBhorg3a4C4l1pLWOt1Ddq5Yvw43FNL_X2LFGNjRdFYv3Oul_5HbmHLN1Ud46h9Q0rQX3$=
    for graphic product...


    LAT...LON 26539933 26909965 28090041 28300043 28460034 28629979
    28669943 28599866 28309806 28149790 27799774 27119776
    26469799 26049830 26099873 26219892 26539933=20

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