• MESO: Mesoscale Discussion 1650

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Mon Aug 30 19:51:14 2021
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    ACUS11 KWNS 301951
    SPC MCD 301950=20

    Mesoscale Discussion 1650
    NWS Storm Prediction Center Norman OK
    0250 PM CDT Mon Aug 30 2021

    Areas affected...Southwestern South Dakota and portions of far
    northern Nebraska and eastern Wyoming

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

    Valid 301950Z - 302145Z

    Probability of Watch Issuance...40 percent

    SUMMARY...A few severe thunderstorms, including supercells, with the
    potential for damaging winds and hail are possible this
    afternoon/evening. A weather watch is being considered.

    DISCUSSION...As of 1930 UTC, visible imagery showed deepening
    updrafts across the Black Hills of far western South Dakota and
    eastern Wyoming. Developing within a weakly forced upper air regime,
    additional surface heating and weak upslope flow are expected to
    support continued destabilization and subsequent thunderstorm
    development this afternoon.=20

    The modified 18z UNR sounding shows an environment potentially
    conducive to organized multicells and supercells, with 1700 J/kg of
    MLCAPE and 31 kt effective shear. Although weak, inhibition of -40
    to -50 J/kg remains across the region, with low-level cumulus still
    absent across far southwestern South Dakota. However, this will
    likely be overcome in the next couple of hours as convective
    temperatures in the mid to upper 80s F are breached by strong
    surface heating. Isolated thunderstorm development is possible by
    late afternoon as the incipient updrafts move out of the Black Hills
    and onto the surrounding High Plains. Favorable CAPE/shear profiles
    and mid-level lapse rates in excess of 8 C/km will support the
    potential for large hail and damaging wind gusts, especially with
    any supercells.=20

    While the environment will remain potentially favorable for severe
    weather, uncertainty remains on the exact spatial coverage of storms
    within the weak forcing regime. Hi-res guidance suggests that at
    least isolated storms will develop and track southeastward into
    northwestern Nebraska this evening. Given the favorable CAPE/shear
    overlap an isolated severe risk for wind and hail would be possible.
    Convective trends are being monitored for a possible weather watch
    despite the uncertainty on storm coverage.

    ..Lyons/Grams.. 08/30/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!sfdto-mx0Wq4gVJDP9SGhSsx-yNYAIFE74jmQkv5zLALL3In_sk-Cc-9HnLg5fvHPExcVTzP$=
    for graphic product...


    LAT...LON 44790333 44600236 44130157 43750127 43380097 43020090
    42770100 42420145 42280212 42270267 42590352 42980384
    43420411 44030425 44440421 44670399 44790333=20

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