• MESO: Mesoscale Discussion 1341

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sat Jul 24 20:01:11 2021
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    ACUS11 KWNS 242001
    SPC MCD 242000=20

    Mesoscale Discussion 1341
    NWS Storm Prediction Center Norman OK
    0300 PM CDT Sat Jul 24 2021

    Areas affected...Parts of southern Lake Michigan...northern Illinois
    and adjacent northwestern Indiana...into parts of southeastern Iowa

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

    Valid 242000Z - 242200Z

    Probability of Watch Issuance...60 percent

    SUMMARY...Widely scattered to scattered strong thunderstorm
    development appears increasingly possible through 5-7 PM CDT,
    particularly around the Greater Chicago metropolitan area, posing a
    risk for a few strong downbursts.

    DISCUSSION...Deepening convective development is ongoing along a
    zone of boundary-layer confluence near/south of a slowly southward
    advancing convective outflow boundary, with thunderstorms beginning
    to initiate near/northwest of the Greater Chicago metropolitan area.

    This coincides with a low-level thermal ridge axis, along which
    strong daytime heating has contributed to steepening near surface
    lapse rates and mixed-layer CAPE on the order of 2000+ J/kg. This is
    also near the southwestern periphery of larger-scale mid-level
    troughing shifting across and to the east of the Great Lakes
    vicinity, where 30-40 kt northwesterly flow around 500 mb is
    contributing to strong deep-layer shear.

    Although forcing for ascent, particularly in mid/upper levels, may
    only allow for widely scattered thunderstorm development to the
    west-southwest of southern Lake Michigan late this afternoon, much
    of the Greater Chicago metro may be impacted. This could include an
    upscale growing line or clusters of storms with the potential to
    produce at least a few strong downbursts.

    ..Kerr/Hart.. 07/24/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!t9FaT7tzS1NvbqhagyWsG48LEnLOAwRLH2du9qupP_tDvDN7F7WJ3q9IdoqLqqQGzmQiBCDX$=
    for graphic product...


    LAT...LON 41619143 42308965 42558661 41638688 41228927 40569141

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