• MESO: Mesoscale Discussion 1426

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Fri Aug 6 23:08:04 2021
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    ACUS11 KWNS 062308
    SWOMCD
    SPC MCD 062307=20
    NEZ000-SDZ000-070100-

    Mesoscale Discussion 1426
    NWS Storm Prediction Center Norman OK
    0607 PM CDT Fri Aug 06 2021

    Areas affected...Parts of southern South Dakota and northern
    Nebraska

    Concerning...Severe Thunderstorm Watch 409...

    Valid 062307Z - 070100Z

    The severe weather threat for Severe Thunderstorm Watch 409
    continues.

    SUMMARY...The evolution of an increasingly organized convective
    system capable of producing severe hail and strong surface gusts in
    excess of 50 kt appears possible near the South Dakota/Nebraska
    vicinity, into the Valentine vicinity by 8-9 PM CDT. Trends are
    being monitored for the possibility of a new severe weather watch
    east of WW 409.

    DISCUSSION...Stronger thunderstorm development may be consolidating
    a bit west of Chadron NE, near/east of the Wyoming/South
    Dakota/Nebraska border vicinity, aided by weak lower/mid level warm
    advection ahead of an approaching short wave trough. This appears
    focused along the southern periphery of a broad zone of strong
    differential surface heating, beneath the northern/northeastern edge
    of warmer and more strongly capping elevated mixed-layer air.

    Near surface/low-level convergence also appears focused along the
    zone, extending eastward along the South Dakota/Nebraska border
    vicinity. Easterly low-level flow near and north of this boundary
    is contributing to strong deep-layer shear beneath 30+ kt westerly
    500 mb flow, while strongest and deepest boundary-layer mixing has
    occurred along and to the south of the frontal zone.

    Although mixed-layer CAPE is relatively modest to weak across the
    higher plains to the west of Valentine, the environment may still be
    conducive to the evolution of a gradually intensifying and
    organizing thunderstorm cluster through 00-02Z. As this occurs,
    there probably will be increasing potential for convection to
    produce a swath of severe wind gusts in excess of 50 kt, as it
    approaches the Valentine vicinity.

    ..Kerr.. 08/06/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!oy9vTjYh0OHx5krTbAlSAKitvON0MIfoYVFgUEZeqXplerxahPXRG2DQhKNfNoZ5BF0zWTGJ$=
    for graphic product...

    ATTN...WFO...LBF...UNR...CYS...

    LAT...LON 43420327 43700181 43560022 42539995 42440103 42450212
    42490327 42970322 43420327=20



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