• MESO: Mesoscale Discussion 1775

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wed Sep 22 17:09:07 2021
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    ACUS11 KWNS 221709
    SPC MCD 221708=20

    Mesoscale Discussion 1775
    NWS Storm Prediction Center Norman OK
    1208 PM CDT Wed Sep 22 2021

    Areas affected...Portions of eastern OH...western PA...and northern

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

    Valid 221708Z - 221945Z

    Probability of Watch Issuance...40 percent

    SUMMARY...A threat for damaging winds and perhaps a couple of
    tornadoes may increase this afternoon as storms develop. Watch
    issuance is possible.

    DISCUSSION...Partly sunny conditions are present this afternoon
    ahead of a cold front across eastern OH into western PA and
    northern/central WV. With surface dewpoints mainly in the mid to
    upper 60s across the warm sector, continued diurnal heating of this
    moist low-level airmass will likely foster at least weak
    destabilization this afternoon. MLCAPE generally ranging from
    1000-1500 J/kg should develop by peak afternoon heating in a couple
    of hours, even though mid-level lapse rates will remain poor. Both
    low and mid-level southerly winds will strengthen this afternoon
    across the warm sector as a nearly closed upper low moves slowly
    eastward across the OH Valley. Increasing large-scale ascent
    associated with the exit region of a mid/upper-level jet and modest
    low-level convergence along the surface cold front will aid the
    development of scattered to numerous storms this afternoon. Even
    with a largely meridional component to the low/mid-level flow,
    around 40-45 kt of effective bulk shear should support storm
    organization, with both a linear and supercell mode possible.
    Damaging winds should be the main threat if a linear mode along the
    cold front dominates, as some high-resolution guidance suggests. A
    couple of tornadoes may also occur, particularly with any supercell
    that develops where surface winds are backed to a more southeasterly
    component, locally enhancing 0-1 km SRH. Watch issuance is possible
    this afternoon, pending signs of increasing storm coverage and

    ..Gleason/Hart.. 09/22/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!rp_zkarQBXs5H3yT3pOitUR8MuHVdUapkBPKQZhXHuOSQuhMSgMi5nFSj1aRC9loIRXaj1dv$=
    for graphic product...


    LAT...LON 40618173 41688146 41948076 42068017 41077896 40347910
    39417987 38828100 38888168 40618173=20

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