SPC AC 161956

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0156 PM CST Wed Dec 16 2020

   Valid 162000Z - 171200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   COASTAL NORTH CAROLINA...

   ...SUMMARY...
   Isolated strong to severe thunderstorms will remain possible across
   parts of coastal North Carolina and west-central Florida this
   afternoon.

   ...20Z Update...
   An isolated damaging wind and brief tornado threat should continue
   for the next couple of hours along/near the NC Coast and Outer
   Banks. Strong low-level shear is present to the northeast of a
   deepening surface low across this region, which should continue to
   prove favorable for updraft rotation. Although instability should
   remain fairly weak, strong low-level warm/moist advection should
   support surface-based storms where dewpoints can increase into the
   low to mid 60s. Severe probabilities have been adjusted to account
   for the northeastward movement of a band of convection located near
   and north of the surface low. For more information on the short-term
   severe risk across eastern NC, see Mesoscale Discussion 1853.

   Widespread precipitation has limited the degree of instability
   across much of the central FL Peninsula this afternoon. The
   potential for an isolated strong to damaging wind gust should remain
   confined along/near parts of the west-central FL Gulf Coast through
   the remainder of the afternoon as storms move onshore. Upper 60s to
   low 70s surface dewpoints are present across this area and slightly
   greater destabilization has occurred in the presence of moderate
   deep-layer shear.

   ..Gleason.. 12/16/2020

   .PREV DISCUSSION... /ISSUED 1054 AM CST Wed Dec 16 2020/

   ...NC...
   An intense shortwave trough is tracking across the lower MS and TN
   valleys today, with large-scale forcing overspreading much of the
   southeast US.  Surface cyclogenesis is currently occurring off the
   SC/NC coast.  Latest radar loop shows a line of showers and
   thunderstorms developing in vicinity of the surface low/warm front. 
   These storms are expected to track northward today and affect the
   coastal counties of eastern NC.  Most model solutions keep
   surface-based CAPE over the Sound and Outer Banks.  Nevertheless,
   strong vertical shear may support supercell structures in this
   activity, with a risk of locally damaging wind gusts or a brief
   tornado.  This threat should end by 23z as storms move out to sea.

   ...FL...
   Scattered thunderstorms are occurring this morning over the
   northeast Gulf of Mexico, along and ahead of an approaching cold
   front.  There is considerable doubt that storms can maintain this
   strength as they move ashore into west-central FL this afternoon,
   due to the limited moisture/instability over that region.  While a
   storm or two may produce gusty winds, the overall severe threat
   appears marginal.

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