SPC AC 240536

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1236 AM CDT Sat Apr 24 2021

   Valid 241200Z - 251200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM
   SOUTHEASTERN ALABAMA AND THE FLORIDA PANHANDLE EAST TO THE GEORGIA
   AND SOUTHERN SOUTH CAROLINA COASTS......

   ...SUMMARY...
   Scattered severe thunderstorms are expected on Saturday across parts
   of the Southeast. All severe hazards appear possible including large
   to very large hail, damaging wind, and tornadoes.

   ...Synopsis...
   A mid- and upper-level short-wave trough will continue moving
   eastward today, crossing the Mid South and Southeast before reaching
   the Atlantic Coast at the end of the period.  In the wake of this
   feature, low-amplitude ridging will prevail, ahead of the next
   trough which will approach the West Coast late.

   A somewhat ill-defined low is forecast to shift eastward across the
   lower Mississippi Valley and Gulf Coast states through the day,
   before turning northeastward overnight -- crossing the Carolinas and
   reaching a position offshore of the Mid Atlantic Coast by 25/12Z. 
   Widespread convection will occur across the southeastern quarter of
   the country, in conjunction with the advance of this storm system.

   ...Lower MS Valley/Gulf Coast states to the eastern Carolinas...
   A complex scenario is evident today across the Southeast, as
   widespread/ongoing convection -- and attendant/local severe risk --
   will be underway at the start of the period.  The bulk of the
   stronger storms will be occurring in the vicinity of a warm front
   over southern portions of the Gulf Coast states.  Widespread
   weaker/stratiform precipitation to the north will continue to
   reinforce this boundary into the afternoon, likely allowing little
   northward retreat.  As such, a main corridor for severe potential
   will likely exist from southern Alabama and the Florida Panhandle
   eastward to southern South Carolina, as repeated rounds of
   storms/storm clusters cross this region.  A very moist boundary
   layer along and south of the composite synoptic/convective boundary
   will contribute to moderate CAPE, and veering flow with height --
   particularly early in the period -- will support organized/rotating
   storms and complex linear structures, with an all-hazards severe
   risk anticipated locally.  

   With time, CAM runs continue to suggest that a rather well-organized
   bowing cluster should move off the Georgia/South Carolina coasts
   during the afternoon, with low-level flow veering in the wake of
   this initial cluster.  Still, favorably strong deep-layer flow
   behind this convection, across the Gulf Coast States, would support
   organized/severe storms.  A main question is whether -- and to what
   degree -- destabilization can occur north and west of the clusters
   of eastward-moving convection -- i.e. into eastern Mississippi and
   central Alabama.  Models continue to hint that destabilization will
   occur -- sufficient to support new storm development nearer the
   upper trough, but successive runs seem to be slightly less
   aggressive with this development.  Still, will maintain SLGT risk
   across this portion of the area, to reflect this potential.

   Overnight, much of the more vigorous convection will have moved
   offshore, the trailing portion of which should be drifting southward
   across northern Florida.  A few storms may also occur across the
   southern Appalachians and then into the Carolinas vicinity, though
   likely elevated atop a stable boundary layer, and thus with only
   limited severe potential.

   ..Goss/Moore.. 04/24/2021

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