SPC AC 200543

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1243 AM CDT Sat Apr 20 2024

   Valid 201200Z - 211200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF CENTRAL/SOUTH TEXAS AND ACROSS PARTS OF THE SOUTHEASTERN US...

   ...SUMMARY...
   Marginally severe storms capable of strong wind gusts and hail will
   be possible across portions of central and south Texas, and during
   the afternoon from southern Mississippi/Alabama across parts of
   Georgia and into southern South Carolina.

   ...Texas...

   Southern stream remains active early this morning.  One weak
   mid-level disturbance is advancing east across the lower Rio Grande
   Valley, while a second more significant short-wave trough is located
   upstream over the lower CO River Valley/Baja region. This feature is
   forecast to progress into west TX by 21/00z, then deamplify as it
   approaches the upper TX Coast late in the period. Large-scale
   pattern favors surface ridging across the middle of the country and
   a dominant high pressure will remain wedged deep against the higher
   terrain of the Rockies. With time the leading edge of this air mass
   will surge into the lower Rio Grande Valley with the surface front
   expected to move off the lower TX Coast by 21/12z.

   Early in the period, low-level warm advection will focus along a
   corridor arcing from the Edwards Plateau into the Red River region
   of north TX/southern OK. Elevated convection will be common at the
   start of the period. Considerable amount of elevated convection will
   likely persist north of the front through the period, gradually
   sagging south as the short wave approaches and the front advances
   into lower latitudes. Forecast soundings do not exhibit very steep
   low-level lapse rates along/near the front and this should limit
   surface-based convection through the period. Most storms are
   expected to develop north of the boundary. Even so, some risk for
   hail/wind will be noted with thunderstorm clusters. If frontal
   convection can develop there is an outside chance for a brief
   tornado with surface-based supercells.

   ...Southeast...

   Surface front is forecast to be draped across the Carolinas-central
   GA-southern AL/MS early in the period. This boundary will move
   little during the day and will serve as the main focus for
   convective development as boundary layer temperatures warm and
   low-level lapse rates steepen. Forecast soundings suggest convective
   temperatures will be breached by early afternoon and scattered
   thunderstorms are expected to develop. Early-morning water-vapor
   imagery suggests the weak short-wave trough over deep south TX may
   contribute to convection along/near this boundary later today. If
   so, some clustering is possible given the large-scale assistance. At
   this time locally damaging winds appear to be the primary risk.

   ..Darrow/Weinman.. 04/20/2024

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