• MESO: Mesoscale Discussion 1581

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Mon Aug 23 19:18:53 2021
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    ACUS11 KWNS 231918
    SWOMCD
    SPC MCD 231918=20
    ILZ000-MOZ000-232115-

    Mesoscale Discussion 1581
    NWS Storm Prediction Center Norman OK
    0218 PM CDT Mon Aug 23 2021

    Areas affected...Parts of west central into southwestern Illinois
    and adjacent portions of east central Missouri

    Concerning...Severe potential...Watch unlikely=20

    Valid 231918Z - 232115Z

    Probability of Watch Issuance...20 percent

    SUMMARY...There appears at least some possibility for the evolution
    of an increasingly organized cluster of thunderstorms, which could
    pose a risk for potentially damaging wind gusts near or just east of
    the Greater St. Louis metropolitan area by 4-6 PM CDT. It is not
    clear that a severe weather watch will be needed, but trends are
    being monitored.

    DISCUSSION...Thunderstorm activity has recently intensified near the intersection of southward advancing convective outflow and a remnant
    low-level baroclinic zone extending across west central Illinois.=20
    This likely has been aided by inflow of very moist boundary layer
    air (with surface dew points in the mid/upper 70s F), which appears characterized by large CAPE up to around 3000 J/kg. In the presence
    of modest shear, largely due to veering of ambient winds from
    southwesterly in low-levels to westerly in mid-levels, southerly
    low-level system-relative inflow appears moderately strong, on the
    order of 15-20 kts. It appears that this may contribute to
    continuing southward propagation toward at least eastern portions of
    the Greater St. Louis metro area during the next few hours.=20=20

    Latest objective instability analysis suggests that the southward
    propagation will coincide with the axis of largest mixed-layer CAPE,
    along the eastern periphery of warmer and more strongly capping
    elevated mixed-layer air emanating from the Great Plains. Given the
    degree of CAPE, coupled with additional steepening of already
    modestly steep low-level lapse rates, there appears at least some
    potential for further intensification and upscale growth of the
    cluster of thunderstorms, which could be accompanied by increasing
    risk to produce potentially damaging surface gusts.

    ..Kerr/Dial.. 08/23/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!rbhS0b8sRchX6nfk9r9iN3LqQDu095Q7QnBK4vLy6PtnsCzlJcwRo6nyhuww5E6y8VVenr_y$=
    for graphic product...

    ATTN...WFO...ILX...LSX...

    LAT...LON 39708948 38968873 38388992 39409075 39619018 39708948=20



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