• MESO: Mesoscale Discussion 1470

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wed Aug 11 06:21:02 2021
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    ACUS11 KWNS 110620
    SWOMCD
    SPC MCD 110620=20
    INZ000-ILZ000-110815-

    Mesoscale Discussion 1470
    NWS Storm Prediction Center Norman OK
    0120 AM CDT Wed Aug 11 2021

    Areas affected...North-Central/Central IL...Far Northwest IN

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

    Valid 110620Z - 110815Z

    Probability of Watch Issuance...40 percent

    SUMMARY...Thunderstorm development anticipated across
    north-central/central IL and far northwest IN tonight. Some stronger
    storms are possible and convective trends will be monitored for
    potential watch issuance.

    DISCUSSION...Recent IR satellite imagery shows some colder cloud
    tops beginning to emerge along northern edge of low to mid-level
    warm-air advection fostered by the low-level jet emanating out of
    the southern Plains. This low-level jet is expected to spread eastward/northeastward over the next few hours as an low-amplitude
    shortwave trough moves out of the central Plains into IA and
    southern MN. As it does, the continued warm-air advection will
    likely result in convective initiation across central IL. Steep
    mid-level lapse rates remain in place, fostering the potential for
    strong buoyancy as the high theta-e air along the MS River is
    advected northeastward. Effective bulk shear across the region also
    remains strong enough for organization/rotation within any stronger,
    more persistent updrafts. Even so, overall convective evolution
    remains uncertain, particularly across northeast IL and adjacent
    northwest IN where the low-level air mass has been stabilized by
    earlier storms.=20

    Given the anticipated elevated character of the storms, large hail
    appears to be the main severe threat. A strong cold pool could
    theoretically penetrate the low-level stability and produce gusts at
    the surface, but the development of such a cold pool would be
    dependent on organization into a convective line, which is uncertain
    at this time. Overall trends will be monitored closely for enough
    storm strength and coverage to merit a watch.

    ..Mosier/Guyer.. 08/11/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!spZ_W2BD3nFVulxwjmDIcHJoaG5JVb4KfKFhXEXugqDSrV8CC5sW49wsyhpPDbYPVyur7JK9$=
    for graphic product...

    ATTN...WFO...IWX...IND...LOT...ILX...DVN...

    LAT...LON 40378995 40569106 41469047 41758968 41628793 41518739
    41188695 40338704 40138760 40308904 40378995=20



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