• MESO: Mesoscale Discussion 1455

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tue Aug 10 01:33:59 2021
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    ACUS11 KWNS 100133
    SWOMCD
    SPC MCD 100133=20
    ILZ000-100300-

    Mesoscale Discussion 1455
    NWS Storm Prediction Center Norman OK
    0833 PM CDT Mon Aug 09 2021

    Areas affected...Parts of north central Illinois

    Concerning...Tornado Watch 417...

    Valid 100133Z - 100300Z

    The severe weather threat for Tornado Watch 417 continues.

    SUMMARY...The risk for tornadoes has diminished considerably.=20
    Continuing severe weather potential remains more unclear, but there
    still appears at least some potential for intensifying thunderstorm
    development and the formation of a cluster of storms to the north of
    Peoria into the 9-11 PM CDT time frame. This could eventually pose
    increasing potential for strong wind gusts, but it remains unclear
    whether a new severe weather watch will be needed.

    DISCUSSION...A lower/mid-level low over eastern Wisconsin is
    forecast to continue to slowly migrate northeastward this evening,
    into a more stable environment across the Great Lakes region.=20
    However, on the southwestern flank of the mid-level troughing,
    low-level warm advection will persist through this evening across
    north central Illinois, where the boundary-layer remains very moist
    and characterized by large CAPE in excess of 3000-4000 J/kg.

    Strong thunderstorm development is ongoing along a low-level
    confluence zone north of Peoria, with perhaps some continuing
    increase in coverage underway. This appears to be occurring in the
    presence of at least modest deep-layer shear, beneath 30 kt
    northwesterly flow around 500 mb. This is contributing to a
    southward propagation of activity, and moderate southerly inflow of
    the potentially strongly buoyant low-level air. At the same time,
    however, warmer and more strongly capping elevated mixed layer air
    is in the process of advecting eastward into the region, and could
    suppress convective development.

    So, subsequent convective developments remain uncertain, and
    probably hinge of the strength of the surface cold pool ongoing
    storms are able to generate in the next hour or two. If a
    developing cold pool is able to maintain convective development,
    there appears potential for an upscale growing, southward
    propagating cluster that could pose increasing potential for strong
    surface gusts.

    ..Kerr.. 08/10/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!rnRoZ34xwyGVzgiwGNEQgbNlBmlSAnvj0wsr5oL5PasKcvnaY8NBMapP32xPNIBEQVVBtOPW$=
    for graphic product...

    ATTN...WFO...LOT...ILX...DVN...

    LAT...LON 41209038 41478950 41478898 41368844 40738836 40448963
    40659037 41209038=20



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