• MESO: Mesoscale Discussion 1555

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wed Aug 18 19:30:17 2021
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    ACUS11 KWNS 181930
    SWOMCD
    SPC MCD 181929=20
    PAZ000-MDZ000-DCZ000-VAZ000-WVZ000-182100-

    Mesoscale Discussion 1555
    NWS Storm Prediction Center Norman OK
    0229 PM CDT Wed Aug 18 2021

    Areas affected...Central/eastern PA...northern
    VA...MD...DC...eastern WV Panhandle

    Concerning...Tornado Watch 447...

    Valid 181929Z - 182100Z

    The severe weather threat for Tornado Watch 447 continues.

    SUMMARY...The tornado and damaging-wind threat will continue to
    gradually increase this afternoon.

    DISCUSSION...While cells with occasional weak rotation have been
    noted recently across central PA and northern MD, supercell
    structures have this far struggled to be sustained across WW 447.
    Earlier discrete cells may have struggled to mature in the midlevel
    dry slot (noted in WV imagery), but renewed development may be more
    vigorous this afternoon as the dry slot shifts eastward and ascent
    associated with the primary midlevel vorticity maximum spreads over
    the region.=20

    Low-level shear/SRH remains sufficient to support some tornado
    threat with any sustained supercell. The greatest relative tornado
    risk may reside across central PA in the vicinity of the
    increasingly diffuse warm front, as convection deepens to the south
    and moves through the baroclinic zone this afternoon. However, any
    sustained cell within the warm sector will also pose some threat.
    Locally damaging wind gusts will also remain possible, especially in
    areas where some steepening of low-level lapse rates has occurred.

    ..Dean.. 08/18/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!va9f6KohivKD9qNXmoECstfSN9vT46kat8HyiAT-3xLsEId-7PizzPY_I3JLJGLQgviTAQPQ$=
    for graphic product...

    ATTN...WFO...PHI...BGM...CTP...LWX...

    LAT...LON 39697854 40127844 40867847 41357793 41757700 41707616
    41537530 41327509 40817517 39737580 39067618 38737742
    39137851 39457848 39697854=20



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