• MESO: Mesoscale Discussion 1759

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Thu Sep 16 20:47:30 2021
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    ACUS11 KWNS 162047
    SPC MCD 162047=20

    Mesoscale Discussion 1759
    NWS Storm Prediction Center Norman OK
    0347 PM CDT Thu Sep 16 2021

    Areas affected...northeast and central MN

    Concerning...Severe potential...Watch likely=20

    Valid 162047Z - 162245Z

    Probability of Watch Issuance...80 percent

    SUMMARY...Severe thunderstorms are expected by 22-23z. Large hail,
    damaging gusts and a couple of tornadoes will be possible with this
    activity. A watch likely will be needed in the next couple of hours.

    DISCUSSION...Stronger heating on the southern edge of thicker
    stratus across central MN has resulted in temperatures warming into
    the mid 80s to near 90 F amid low/mid 60s F dewpoints. Modified
    forecast soundings for current observations show inhibition has
    nearly eroded across this region. Visible satellite imagery further
    indicates inhibition has rapidly eroded as CU field across the area
    has become more agitated with vertical development over the past
    hour or so. While CAMs guidance suggest convective initiation may
    not occur until closer to 00z, observational trends suggest storms
    could develop sooner.=20=20

    Steep midlevel lapse rates atop a moist boundary layer are aiding in
    generally 1000-2000 J/kg MLCAPE across the warm sector ahead of a east/southeast moving cold front. Strong vertical shear already is
    in place, with effective shear magnitudes around 35-50 kt. This
    parameter space will support initial supercells, though deep-layer southwesterly flow parallel to the surface front could result in
    evolution of a messy storm mode with time via outflow interactions.
    Large hail (especially with discrete convection), damaging gusts and
    a tornado or two are possible through this evening.

    ..Leitman/Hart.. 09/16/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!v3WuoA7ncgZpeUMEPCYteS2P-y7bQTS-pGdWrXNLBd-BqTUKb-CNSPZm3mTSxakpKM8MpHNr$=
    for graphic product...


    LAT...LON 45459261 44999326 44719390 44589449 44639516 44779565
    45059594 45409594 45929565 46979496 48109402 48569335
    48649299 48689236 48599163 48349126 48099100 47749091
    47479106 46209199 45459261=20

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