• MESO: Mesoscale Discussion 0671

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tue May 18 18:18:47 2021
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    ACUS11 KWNS 181818
    SWOMCD
    SPC MCD 181818=20
    TXZ000-182015-

    Mesoscale Discussion 0671
    NWS Storm Prediction Center Norman OK
    0118 PM CDT Tue May 18 2021

    Areas affected...Portions of south-central into east-central/coastal
    TX

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

    Valid 181818Z - 182015Z

    Probability of Watch Issuance...60 percent

    SUMMARY...A threat for large hail, damaging wind gusts, and perhaps
    a couple of tornadoes should increase this afternoon. Watch issuance
    will probably be needed.

    DISCUSSION...As of 1815Z an outflow boundary from earlier convection
    extends from parts of south-central into east-central TX. Recent
    visible satellite imagery shows this boundary has slowed, and it may
    not make much more southeastward progress this afternoon. Mostly
    clear skies ahead of the outflow boundary have allowed robust
    diurnal heating to occur, with surface temperatures generally
    warming into the low to mid 80s. A rather moist low-level airmass
    characterized by surface dewpoints in the mid to upper 60s also
    exists across this region. Continued heating of this moist airmass
    coupled with somewhat steepened mid-level lapse rates will likely
    support MLCAPE of 1500-2500 J/kg by late afternoon. Around 25-35 kt
    of southwesterly mid-level flow associated with an upper low over
    the southern/central High Plains should foster similar values of
    deep-layer shear. Current expectations are for storms to gradually
    increase in both coverage and intensity along/near the outflow
    boundary this afternoon as convective inhibition continues to erode.
    A mixed mode of supercell and multicell structures appears likely,
    with both large hail and damaging wind gusts possible. Storms may
    have a tendency to congeal into a bowing cluster with time, and
    severe/damaging winds may eventually become the main threat. Some
    risk for a couple of tornadoes could also exist with storms near the
    outflow boundary where low-level flow and shear may be modestly
    enhanced. A watch will probably be needed in the next couple of
    hours, dependent on convective trends.

    ..Gleason/Guyer.. 05/18/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!rBk5bgsV45mHnA9xOBVwfyXTTvpP4sMGXjs0i_3DCrpEC6i18n7s0jCnv82doGLit-vmbbKy$=
    for graphic product...

    ATTN...WFO...HGX...FWD...CRP...EWX...

    LAT...LON 29149642 28379788 28399855 29379916 29929899 30189823
    30589726 31129664 31679593 31689546 31359503 30959481
    29919537 29149642=20



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