SPC AC 160800

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0200 AM CST Tue Nov 16 2021

   Valid 181200Z - 191200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   Severe thunderstorms are not forecast across the contiguous United
   States on Thursday.

   ...Synopsis and Discussion...
   Isolated thunderstorms may be ongoing at the start of the period
   Thursday morning along/near a cold front across parts of Deep South
   TX and coastal LA/MS. This front is expected to continue advancing
   southward over the Gulf of Mexico through the day, which should
   quickly end thunderstorm chances across both areas. Farther north, a
   large-scale upper trough/low should move from Ontario into Quebec
   through the period, while the southern portion of the trough
   develops eastward from the Great Lakes/OH Valley across the
   Mid-Atlantic and Northeast. The primary surface low will remain
   displaced well to the north of these regions in Canada. A cold front
   arcing southward from this low is expected to sweep eastward across
   much of the eastern CONUS through the day, and north FL Thursday
   night.

   Boundary-layer moisture will probably remain rather modest ahead of
   the front along most of the East Coast, as a prior frontal passage
   should limit potential for more robust return flow from either the
   Gulf of Mexico or tropical Atlantic. This should hamper the
   development of sufficient instability to support thunderstorms along
   much of the front on Thursday, with the possible exception of
   coastal NC/SC where convection may develop late. Still, there will
   be strong flow at low/mid levels associated with the upper trough
   that will overspread much of the Mid-Atlantic. If even a small
   amount of boundary-layer instability can be realized, then
   strong/gusty winds could occur with low-topped convection along the
   front. At this point, latest guidance continues to suggest that
   instability will remain too meager to support storms, with the
   previously mentioned exception in coastal NC/SC. Otherwise,
   thunderstorms will be possible Thursday across much of central/south
   FL, where greater low-level moisture will reside. Poor mid-level
   lapse rates and the lack of stronger flow below 500 mb should
   greatly limit the severe threat across this area.

   ..Gleason.. 11/16/2021

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