SPC AC 140810

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0210 AM CST Mon Dec 14 2020

   Valid 161200Z - 171200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS WEDNESDAY ACROSS
   PARTS OF EASTERN NORTH CAROLINA AND THE NORTHERN FLORIDA PENINSULA
   GULF COAST...

   ...SUMMARY...
   Strong thunderstorms may impact parts of the Outer and Inner Banks
   vicinity of North Carolina and Gulf coastal areas of the northern
   Florida Peninsula Wednesday, posing at least some risk for severe
   weather.

   ...Synopsis...
   Little change in the general large-scale pattern is expected from
   Tuesday into Wednesday.  Stable conditions will prevail across much
   of the U.S., except along a northwestward sloping frontal zone
   extending across the middle and southern Atlantic Seaboard into the
   northeastern Gulf of Mexico.  Aside from parts of northern
   Florida/the northern Florida Peninsula, the surface front is
   expected to mostly remain offshore.  However, moisture return above
   the frontal inversion, inland of coastal areas, may contribute to
   areas of very weak CAPE.  This may contribute to at least low
   probabilities for convection capable of producing lightning, as a
   vigorous remnant short wave perturbation rapidly accelerates
   northeast of the lower Mississippi Valley.

   Initially, there may be a couple of developing waves along the
   frontal zone, one over the northeastern Gulf of Mexico and another
   off the South Carolina coast.  However, as the mid-level
   perturbation approaches the Mid Atlantic coast, the trailing wave is
   expected to weaken as the lead wave becomes more prominent. 
   Substantive further deepening is forecast as a developing cyclone
   center tracks near or across the North Carolina Outer Banks vicinity
   into areas off the Mid Atlantic coast by Wednesday evening.

   ...Eastern North Carolina...
   There appears at least some possibility that the track of the
   developing cyclone may allow for at least a weakly destabilizing
   warm sector boundary layer to overspread the Outer and Inner Banks
   vicinity by Wednesday afternoon.  If this occurs, it probably will
   be in the presence of wind profiles characterized by strong
   deep-layer shear and sizable, clockwise curved low-level hodographs,
   supportive of supercell convection posing potential to produce a
   tornado or damaging wind gusts.

   ...Northern Florida/Florida Peninsula...
   A signal exists in the latest model output that a cluster of
   thunderstorms will spread into coastal areas by Wednesday afternoon.
   Initially supported by moderate boundary-layer CAPE over the
   northeastern Gulf of Mexico, an organized line of vigorous
   thunderstorms may develop along the leading edge of this cluster, in
   the presence of sheared, 30-50+ kt west-southwesterly deep-layer
   mean flow.  Although the environment may become progressively less
   stable into coastal areas, with instability inland also remaining
   poor, it is possible that a damaging wind/isolated tornado risk
   could at least develop into coastal areas between Tampa and the Big
   Bend vicinity, before diminishing.

   ..Kerr.. 12/14/2020

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