• MESO: Mesoscale Discussion 0450

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wed Apr 28 17:07:03 2021
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    ACUS11 KWNS 281706
    SWOMCD
    SPC MCD 281706=20
    NYZ000-PAZ000-OHZ000-281900-

    Mesoscale Discussion 0450
    NWS Storm Prediction Center Norman OK
    1206 PM CDT Wed Apr 28 2021

    Areas affected...Portion of northwest Pennsylvania...southwest New York...northeast Ohio

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

    Valid 281706Z - 281900Z

    Probability of Watch Issuance...40 percent

    SUMMARY...The severe threat is gradually increasing across eastern
    portions of the Lower Great Lakes region. Damaging wind gusts and
    large hail are expected to be the primary severe threats. Conditions
    are currently being monitored for the possibility of a Severe
    Thunderstorm Watch issuance.

    DISCUSSION...Diurnal heating, and the northeastward advection of
    modest low-level moisture (characterized by near 60F dewpoints per
    latest METAR observations) are resulting in increased instability
    across eastern portions of the Lower Great Lakes this afternoon.
    Modifying RAP forecast soundings to current surface
    temperature/dewpoint fields yields 500/1000 J/kg of SBCAPE/MLCAPE.
    The 1630Z BUF-VWP shows modestly curved low-level hodographs, with
    over 200 m2/s2 0-3 km SRH and 30+ kts of deep-layer shear present.
    Current MRMS Mosaic radar data shows organized convection crossing
    Lake Erie and is poised to reach Erie and Chautauqua Counties in NY
    within the hour. Additional convective development is also possible
    over the next few hours.

    Storms that can mature and become sustained in the current
    environment will likely be multicellular in nature, with one or two
    of the stronger, longer lived complexes potentially supporting the
    development of transient supercellular or small-scale bowing
    structures. With continued surface heating, a well-mixed sfc-850 mb
    layer will likely support damaging gusts with the stronger storms.
    Latest Mesoanalysis also shows 7-7.5 C/km mid-level lapse rates
    present, supporting the risk for large hail, especially with any
    bowing segments or supercells that develop. Given the modest
    low-level veering with height, a brief tornado also cannot be
    completely ruled out.

    Convective coverage and subsequent severe remains a bit uncertain at
    this time. Trends will continue to be monitored for the need of a
    Severe Thunderstorm Watch issuance.

    ..Squitieri/Hart.. 04/28/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!u2F_D8H-bmei7zme2cCdyaifyyNZy19P-EuMacKKsHSgmMB1DTgEiXma607-z4hy_vxztpv1$=
    for graphic product...

    ATTN...WFO...BGM...BUF...CTP...PBZ...CLE...

    LAT...LON 41818105 43087873 43417680 43267597 42397595 41577660
    40847775 40747893 40947996 41418098 41818105=20



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