• MESO: Mesoscale Discussion 1487

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wed Aug 11 20:56:47 2021
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    ACUS11 KWNS 112056
    SWOMCD
    SPC MCD 112056=20
    ILZ000-IAZ000-MOZ000-112330-

    Mesoscale Discussion 1487
    NWS Storm Prediction Center Norman OK
    0356 PM CDT Wed Aug 11 2021

    Areas affected...Portions of eastern IA...far northeastern MO...and northwestern IL

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

    Valid 112056Z - 112330Z

    Probability of Watch Issuance...40 percent

    SUMMARY...If storms develop and can be sustained, then the threat
    for large hail and damaging winds would increase. Convective trends
    will be closely monitored, with watch issuance possible.

    DISCUSSION...Recent attempts at convective initiation have been
    noted across eastern IA along/east of a surface cold front. This
    region is on the southern extent of an upper trough over central
    Canada and the Upper Midwest, with minimal mid-level height falls
    noted. Still, latest mesoanalysis suggests that airmass just ahead
    of the front is extremely unstable and uncapped, with MLCAPE of
    3500-4500 J/kg present. Latest VWP from KDVN shows winds veering
    with height through mid levels and strengthening to around 45-50 kt
    above 3 km. Related 35-40 kt of deep-layer shear would be supportive
    of supercells. The presence of steep mid-level lapse rates and a
    very favorable thermodynamic environment suggests a threat for large
    hail with any supercell that can form and be sustained. Damaging
    downdraft winds would also be a concern. The main question is
    whether any robust storms will be able to form given the weak
    large-scale ascent aloft. This region will be closely monitored for
    signs of increasing convective coverage/intensity, with watch
    issuance possible.

    ..Gleason/Thompson.. 08/11/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!usOHplgRcdB6GWr5KfQ93L2upWYY8ijm-oDfvVwXi-kkrV4-zvUU4BnNPwHTfQKi0DzLdXoK$=
    for graphic product...

    ATTN...WFO...ILX...LSX...DVN...DMX...EAX...

    LAT...LON 42569181 42569103 42318996 41858989 41039014 40339104
    40209211 40259298 41129292 42139242 42569181=20



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