SPC AC 290600

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1200 AM CST Sun Nov 29 2020

   Valid 291200Z - 301200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL
   AND EASTERN GULF COAST REGION...AND THE SOUTHEASTERN U.S. ATLANTIC
   COAST...

   ...SUMMARY...
   Isolated strong to severe thunderstorms remain possible today and
   tonight across southern portions of the Gulf Coast states into the
   eastern Carolinas.  A couple of tornadoes, and a few locally
   damaging wind gusts, are the main threats.

   ...Synopsis...
   An upper low initially over Oklahoma is forecast to move eastward to
   the mid/lower Mississippi Valley through the first half of the
   period, but will gradually become absorbed by a northern-stream
   trough digging east-southeastward out of the northern Plains/upper
   Mississippi Valley into the Midwest/middle Mississippi Valley
   overnight.

   At the surface, a weak low is forecast to move across the northern
   Gulf of Mexico near the Louisiana coast toward Mobile Bay during the
   day, along a pre-existing baroclinic zone.  Thereafter, the low is
   progged to turn northeastward and move quickly northward along the
   Appalachians, deepening rapidly as it reaches the West Virginia
   vicinity by the end of the period/Monday morning. 

   ...Central and eastern Gulf Coast/southeastern Atlantic coast...
   Widespread precipitation is forecast to be ongoing at the start of
   the period ahead of the advancing upper low, from southern and
   eastern Texas across Arkansas and Louisiana into southern
   Mississippi and vicinity.  The substantial precipitation and cloud
   cover -- that should persist through the day -- over the central
   Gulf Coast states/mid South should maintain a stable boundary layer.
    Any potential for surface-based convection appears likely to remain
   confined to southeast Louisiana, southeast Mississippi, and into
   southern Alabama and the Florida Panhandle through the daylight
   hours.  A separate area of storms may evolve during the afternoon
   across eastern South Carolina and into the southern Atlantic, near a
   developing warm front.  

   During the evening and overnight, as the surface low deepens/shifts
   rapidly north-northeastward, surface-based convection will spread
   eastward across southeastern Alabama and roughly the southern half
   of Georgia, and northern portions of the Florida Peninsula ahead of
   the strengthening cold front.  Meanwhile, surface-based convection
   will shift northward across the eastern Carolinas and eventually
   into southeastern Virginia, east of the surface low as the warm
   front shifts northward.

   Instability is forecast to remain quite limited inland, with
   generally less than 300 to 500 J/kg mixed-layer CAPE expected. 
   However, increasingly strong and veering flow with height will
   evolve with time, in tandem with surface cyclogenesis, yielding
   shear profiles sufficient for supercells.  While modest CAPE should
   remain a limiting factor, a couple of tornadoes will be possible,
   within a broad SLGT risk area from southern Mississippi east to
   northern Florida, and north across the eastern Carolinas to
   southeast Virginia.  A few stronger storms may also produce
   gusty/locally damaging winds, particularly if small bowing segments
   can evolve locally.  Risk will taper off from west to east along the
   Gulf Coast through the evening, but may linger through the end of
   the period across portions of Florida, and particularly along the
   Atlantic Coastal portion of the outlook.

   ..Goss/Moore.. 11/29/2020

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