SPC AC 241952

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0152 PM CST Thu Dec 24 2020

   Valid 242000Z - 251200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE EASTERN CAROLINAS AND SOUTHEASTERN VIRGINIA...

   ...SUMMARY...
   Severe risk -- which includes potential for locally damaging winds
   and a few tornadoes -- continues across portions of the Carolinas
   and Mid-Atlantic region, and to a lesser degree southward into
   Florida.

   ...Discussion...
   Few changes appear necessary to the ongoing outlook at this time, as
   convection continues to evolve as expected.  The primary change has
   been to remove the SLGT risk area centered over the Florida
   Panhandle, as the main convective band has now moved through the
   area of relatively greater CAPE.  Though isolated severe risk will
   continue across Florida and southeastern Georgia, greater risk
   remains farther to the north across the eastern Carolinas and
   southeastern Virginia.  Bands of pre-frontal convection will
   increase over the next few hours, with an associated uptick in
   severe/tornado potential expected.  Later, a frontal band of
   convection is forecast to organize and shift eastward across this
   region, accompanied by risk for damaging winds and a tornado or two
   before moving offshore.

   ..Goss.. 12/24/2020

   .PREV DISCUSSION... /ISSUED 1030 AM CST Thu Dec 24 2020/

   ...Eastern/central Carolinas and Mid-Atlantic States...
   Multi-round severe convection is possible across parts of the region
   this afternoon into tonight, particularly for the eastern
   Carolinas/southeast Virginia, where semi-discrete warm sector storms
   this afternoon/early evening could be followed by a well-organized
   convective line late this evening and early in the overnight.

   Multi-layer cloud cover remains prevalent at midday across the
   region with air mass modification occurring near the coastal
   Carolinas where low/middle 60s F surface dewpoints are becoming more
   prevalent. North/northeastward-racing bands of convection over the
   eastern Carolinas will persist through the afternoon where the
   convection should gradually intensify as it becomes rooted within
   the increasingly moist/unstable boundary layer, although the
   persistent cloud cover and the possibility of a lingering warm layer
   aloft leads to some temporal uncertainty. Regardless, extremely
   strong low-level/deep-layer shear, accentuated by 55-60 kt in the
   lowest 1 km AGL and 300+ 0-1 km SRH, will be supportive of
   fast-moving supercells capable of a tornado/damaging wind risk,
   particularly late this afternoon through early evening. Given the
   magnitude of the vertical shear/SRH, a strong tornado cannot be
   ruled out.

   Otherwise, as previously mentioned, an additional round of regional
   severe risk will likely occur this evening into the overnight as a
   strongly forced convective line evolves and spreads
   east-northeastward across the Carolinas and coastal
   Mid-Atlantic/Delmarva. Damaging winds are the most probable severe
   hazard, although a QLCS-related tornado risk may exist as well.

   ...Florida/Georgia...
   A northeast/southwest-oriented composite convective line across
   southern Georgia/Florida Panhandle at late morning immediately
   precedes an eastward-moving cold front. Some additional
   moistening/diurnal destabilization will occur across the Florida
   Peninsula into far southern Georgia ahead of the front/convective
   line, with surface-based destabilization otherwise remaining minimal
   farther north into central/eastern Georgia. Low-level/deep-layer
   winds will further strengthen across the region, although low-level
   winds will tend to slowly veer with wind profiles trending more
   unidirectional over time. Even with relatively modest buoyancy, this
   scenario will support further organization and development of
   upscale-growing quasi-linear convective bands this afternoon. An
   isolated damaging wind/tornado risk will exist across the region
   through the afternoon, with the overall severe risk shifting
   eastward/tending to diminish toward and after sunset.

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