• MESO: Mesoscale Discussion 0619

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sat May 15 18:17:28 2021
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    ACUS11 KWNS 151817
    SPC MCD 151816=20

    Mesoscale Discussion 0619
    NWS Storm Prediction Center Norman OK
    0116 PM CDT Sat May 15 2021

    Areas affected...Central Iowa into portions of Minnesota and

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

    Valid 151816Z - 152015Z

    Probability of Watch Issuance...20 percent

    SUMMARY...Isolated thunderstorms are expected to develop along a
    wind shift boundary within the next 1 to 2 hours and pose a low-end
    risk for severe hail/gusty winds. Low coverage and uncertainty in
    the severity of the expected storms suggests a weather watch is

    DISCUSSION...As of 1730 UTC, visible satellite data showed a
    deepening cumulus field with several taller towers ahead of a
    shortwave trough across north-central Iowa and southern Minnesota.
    Surface observations indicate the presence of a wind-shift boundary
    aiding in localized low-level convergence near the Iowa-Minnesota
    border. With additional heating and weak background lift from the
    slow moving trough expected in the next few hours over the already
    warm and modestly moist airmass, (temps in the 70s F with dewpoints
    near 50 F), isolated thunderstorm development appears likely. While
    upper-level flow will not be overly strong, SPC mesoanalysis shows
    between 30 and 40 kts of effective shear will be colocated with
    250-500 J/kg of MLCAPE. A few multi-cell storms or weak supercells
    will be capable of producing marginally severe hail or gusty outflow
    winds this afternoon.=20

    Downstream across portions of eastern Iowa and Wisconsin, widespread
    cloud cover and precipitation have resulted in a cool and stable
    boundary layer. Thus, a relatively narrow corridor of
    destabilization exists, suggesting the greatest threat for any
    severe weather will be confined to portions of north-central Iowa
    and southeastern Minnesota this afternoon before storms encounter a
    much more hostile environment early this evening. Given the limited
    spatial and temporal threat, a weather watch is unlikely.

    ..Lyons/Guyer.. 05/15/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!p0ezAYzZNMscEhxT5EO2l8XHmwLgrq0veuAuKvEZs9Jn-8EhqakQsXml-KftRhgzPTlbPJNy$=
    for graphic product...


    LAT...LON 41229492 41609547 41999560 42649555 43219530 43789445
    44559388 45319360 45709300 45289234 44659209 43339194
    42519196 41969245 41569333 41349391 41229492=20

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