• MESO: Mesoscale Discussion 1582

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Mon Aug 23 19:57:22 2021
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    ACUS11 KWNS 231957
    SWOMCD
    SPC MCD 231956=20
    SDZ000-NEZ000-232200-

    Mesoscale Discussion 1582
    NWS Storm Prediction Center Norman OK
    0256 PM CDT Mon Aug 23 2021

    Areas affected...Parts of south central South Dakota and adjacent
    north central Nebraska

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

    Valid 231956Z - 232200Z

    Probability of Watch Issuance...40 percent

    SUMMARY...Isolated supercell development, posing a risk for large
    hail and strong downbursts, is possible across parts of south
    central South Dakota, including areas near or south of Pierre,
    through 4-6 PM CDT. It is not yet certain that a severe weather
    watch will be needed, but trends are being monitored for this
    possibility.

    DISCUSSION...Deepening convective development is evident southeast
    of Philip, SD, near a zone of enhanced low-level confluence and
    convergence, within general surface troughing encompassing much of
    the Great Plains. This is also near the southwestern flank of a
    low/mid-level wind shift, which demarcates the northern fringe of
    deeper low-level moisture/higher precipitable water, which is
    forecast to begin returning northeastward late this afternoon.=20=20

    The higher moisture content is contributing to sizable CAPE on the
    order of 2000-3000 J/kg, beneath warm and capping elevated
    mixed-layer air. With mid-levels temperatures tending to warm above
    the retreating low-level wind shift, it is not certain that ongoing
    attempts at deep convective development will be able to overcome
    mid-level inhibition. However, forcing aloft associated with an
    upstream perturbation emanating from the Rockies could provide
    additional support for this during the next few hours.=20=20

    If thunderstorm development is able to initiate and be maintained,
    deep-layer shear, beneath a 30-40+ kt west-southwesterly 500 mb jet
    streak propagating across the region, is strong and supportive of
    supercells capable of producing large hail and strong downbursts.

    ..Kerr/Dial.. 08/23/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!rY1pv2tsdQxn-0u5s7iOYWYtBEn6OUB-K8WYktKu5Ck5VN2sHNWc_zsQPYF7XbexNz7lXsuU$=
    for graphic product...

    ATTN...WFO...FSD...ABR...LBF...UNR...

    LAT...LON 43970157 44339968 43769813 42939879 43020103 43970157=20



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