SPC AC 201950

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0250 PM CDT Sat Apr 20 2024

   Valid 202000Z - 211200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
   THE SOUTHEAST...AND INTO CENTRAL AND SOUTHERN TEXAS...

   ...SUMMARY...
   Marginally severe storms capable of strong wind gusts and hail will
   be possible mainly this afternoon/evening across portions of central
   and south Texas, and from southern Mississippi to southern North
   Carolina.

   No changed required for the 20Z update.

   For more information see mesoscale discussion 498, 499, 500.

   ..Jewell.. 04/20/2024

   .PREV DISCUSSION... /ISSUED 1112 AM CDT Sat Apr 20 2024/

   ...Synopsis...
   Mid-morning radar mosaics show a broad swath of elevated convection
   ongoing across the southern Plains ahead of an approaching
   upper-level wave. While a few instances of gusty winds and/or
   sub-severe hail will be possible with this activity, a slightly more
   robust severe threat will be focused along a surface cold front
   recently analyzed from the southern Appalachians to southern TX.
   Surface high pressure is expected to build east into the Plains/MS
   Valley through the day, which will nudge the cold front slowly
   southward over the next 24 hours. Isolated to scattered
   thunderstorms are expected to develop along this boundary by
   mid-afternoon with a few strong/severe storms possible. 

   ...Southern Gulf states to the Southeast...
   Mostly clear to partly cloud skies are noted along and ahead of the
   cold front from SC into southern AL/MS. Diurnal warming of a
   modestly moist air mass should yield MLCAPE values upwards of 1000
   J/kg by early to mid-afternoon. Despite minimal inhibition, weak
   forcing for ascent along the front should support isolated to widely
   scattered thunderstorms. Storm motions largely along the boundary
   should support initial cells growing upscale into clusters through
   the afternoon/evening. While low to mid-level winds are modest,
   30-40 knot flow aloft may support sufficient deep-layer shear for a
   few more organized cells/clusters with an attendant hail risk.
   Damaging outflow gusts are also possible - especially across areas
   where surface temperatures can warm into the mid/upper 80s by peak
   heating. Based on 16 UTC observations, this appears most likely to
   occur across parts of GA into the Carolinas.

   ...Southern Texas...
   Two clusters of thunderstorms appear possible this afternoon and
   evening across southern Texas. Elevated convection developing along
   the western fringe of the synoptic front across the Big Bend region
   of TX should gradually become surface-based as storms migrate east
   into an increasingly buoyant air mass. Thunderstorms should also be
   focused along a more subtle boundary noted along the TX Coastal
   Plain in recent surface analyses. Across both regions, sufficient
   deep-layer shear should be in place to support a few organized
   cells, but mean storm motions and deep-layer shear vectors largely
   along the initiating boundaries should favor convective clusters
   with an attendant hail/wind risk. A low-end tornado threat may
   materialize along the boundary along the Coastal Plain where
   low-level flow should remain backed to the south/southeast, yielding
   effective SRH values between 100-150 m2/s2. However, given the
   potential for upscale growth, this threat is expected to be fairly
   limited.

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