• MESO: Mesoscale Discussion 0452

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wed Apr 28 18:15:01 2021
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    ACUS11 KWNS 281814
    SPC MCD 281814=20

    Mesoscale Discussion 0452
    NWS Storm Prediction Center Norman OK
    0114 PM CDT Wed Apr 28 2021

    Areas affected...Portions of central into north-central TX

    Concerning...Severe potential...Watch likely=20

    Valid 281814Z - 282015Z

    Probability of Watch Issuance...95 percent

    SUMMARY...The threat for large to very large hail, damaging wind
    gusts, and isolated tornadoes should increase this afternoon. Watch
    issuance is likely.

    DISCUSSION...A convectively reinforced outflow boundary has stalled
    across part of central TX this afternoon per recent surface
    observations and visible satellite imagery. The airmass along/south
    of this boundary is becoming moderately unstable, as surface
    temperatures have warmed well into the 80s amidst mid to upper 60s
    dewpoints. Latest mesoanalysis and RAP forecast soundings in the
    vicinity of San Angelo TX suggest minimal convective inhibition
    remains, with MLCAPE in the 1500-2000 J/kg range. As diurnal heating
    of this moist low-level airmass continues, a further increase in
    instability appears likely. Current expectations are for multiple
    storms to initiate along the surface boundary in central TX within
    the next couple of hours as ascent associated with a mid/upper-level
    trough approaches from the west. These storms should subsequently
    move east-northeastward into north-central TX. It is only weakly
    unstable at the moment with northward extent into north-central TX
    due to the influence of earlier convection. Still, some airmass
    recovery appears likely through the remainder of the afternoon
    across this region, as rich low-level moisture remains in place.

    The deep-layer shear is very favorable for organized severe storms,
    with around 50-60 of effective bulk shear in place across the warm
    sector. Supercell structures appear likely with initial development,
    and large to very large hail (2+ inches in diameter) will be a
    threat. This large hail threat should continue into north-central TX
    through the afternoon/early evening, but it probably will be
    dependent on how much airmass recovery/destabilization can occur.
    Isolated straight-line damaging wind gusts also appear possible as
    low-level lapse rates gradually steepen. Finally, there may also be
    a threat for a few tornadoes, even though the stronger low-level
    flow associated with a southerly low-level jet will be shifting
    eastward away from this area. Around 100-150 m2/s2 of effective SRH
    should support some low-level rotation with any discrete supercells.
    Given the expected increase in the overall severe threat this
    afternoon, watch issuance will likely be needed.

    ..Gleason/Hart.. 04/28/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!sEwKTzay5Wl1wUxBkkMiLN3a3CNBTs2NPUI0Rz-m27vgcH73YGsjyOk4mxg3hK0E8jGAWxyj$=
    for graphic product...


    LAT...LON 31439948 31460024 31720063 32020046 32429973 33009891
    33559802 33679753 33689691 33639641 33089663 32579705
    32209752 31849808 31539881 31439948=20

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