• MESO: Mesoscale Discussion 0644

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Thu Apr 27 23:58:15 2023
    ACUS11 KWNS 272358
    SWOMCD
    SPC MCD 272357=20
    ALZ000-MSZ000-TNZ000-ARZ000-280200-

    Mesoscale Discussion 0644
    NWS Storm Prediction Center Norman OK
    0657 PM CDT Thu Apr 27 2023

    Areas affected...Eastern Arkansas to northern Mississippi and
    northwest Alabama

    Concerning...Severe Thunderstorm Watch 176...

    Valid 272357Z - 280200Z

    The severe weather threat for Severe Thunderstorm Watch 176
    continues.

    SUMMARY...The threat for severe hail and damaging winds continues
    across much of WW 176, but the greatest near-term risk will reside
    across eastern Arkansas into northwest Mississippi and far eastern
    Mississippi to far west/northwest Alabama.

    DISCUSSION...Scattered convection continues to erupt immediately
    ahead of a mid-level vorticity maximum traversing across central AR.
    This zone of focused ascent, combined with a favorable thermodynamic
    and kinematic environment, has supported splitting supercells,
    including a more prominent/robust cell across Arkansas/Monroe
    counties that has remained relatively isolated. These cells will
    continue to pose a large hail threat for the next 1-2 hours as they
    move towards the apex of the MLCAPE axis across northwest MS.
    However, long-term trends are somewhat uncertain given consolidating
    convection along an outflow boundary to the west of the more
    discrete activity, and the propensity for storm
    interactions/amalgamating outflows with time within the focused zone
    of ascent. Such upscale growth may favor an increasing damaging wind
    threat, but weak low-level shear (around 20-25 knots in the 0-3 km
    layer) sampled by regional VWPs casts uncertainty onto this
    scenario.

    To the east along the MS/AL border, a pair of long-lived supercells
    with a history of 1-1.75 inch hail will begin to gradually meander
    into the periphery of the higher mixed-layer buoyancy as they
    migrate into western AL. However, the isolated nature of the
    convection combined with 40-45 knots of effective bulk shear
    downstream should help maintain storm intensity and the associated
    large hail threat for the next few hours. Elsewhere across WW 176, environmental parameters remain conducive for organized convection,
    but additional CI is uncertain. The most likely location for
    near-term CI appears to be across northwest MS where the GOES day
    cloud phase RGB and low-level water vapor imagery shows shallow
    convective towers, but robust convective initiation remains
    uncertain given the onset of diurnal cooling.

    ..Moore.. 04/27/2023

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!8J18pgR2QNqaIua5SmpdeqydFUR_oBckpQI1Jdwy_Xw7PhiqphzBUxzUWMOb4IxGcOHLaOcBV= kwKnhourKVrxCae4qI$ for graphic product...

    ATTN...WFO...BMX...HUN...MOB...MEG...JAN...LZK...

    LAT...LON 33429120 33699189 34499215 35239203 35569137 35669044
    35428916 34868835 34138728 33878712 33548705 33138722
    32758762 32398807 32158870 32248922 32498947 33429120=20


    =3D =3D =3D
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