SPC AC 170624

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1224 AM CST Wed Nov 17 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 to scattered thunderstorms will probably be ongoing
   Thursday morning along and near a cold front across parts of Deep
   South TX and the lower MS River Valley. Plentiful low-level moisture
   will be present along/south of the front in TX, which should support
   weak to locally moderate instability. Regardless, modest
   low/mid-level winds will likely temper the severe threat. As the
   cold front continues to advance southward into the Gulf of Mexico,
   thunderstorm chances should quickly wane by late Thursday morning
   across both regions. Farther north, an upper trough/low will move
   from Ontario into Quebec through the period, while the southern
   portion of the trough advances 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 states through the period,
   and into north FL by Thursday night.

   Consensus of latest guidance continues to suggest that modest
   low-level moisture should return northward ahead of the front from
   the central Gulf Coast to the Mid-Atlantic. However, due to a prior
   frontal passage, this moisture appears to be shallow, and only low
   to mid 50s surface dewpoints may be present ahead of the front over
   much of the eastern states. This limited low-level moisture coupled
   with poor mid-level lapse rates will likely hinder the development
   of even weak instability across much of the eastern CONUS. One
   possible exception may be across portions of NC/SC and vicinity by
   Thursday evening/night, as upper 50s to lower 60s surface dewpoints
   present across this area may allow for sufficient instability to
   support isolated thunderstorms. Still, even if this convection
   forms, it should be undercut by the quickly moving cold front and
   become elevated. Otherwise, thunderstorms may occur Thursday across
   much of the FL Peninsula, as a weak mid-level disturbance
   overspreads this region. Greater low-level moisture will be present
   here compared to locations farther north, but poor lapse rates and
   weak flow below 500 mb suggest that the overall severe threat should
   remain low.

   ..Gleason.. 11/17/2021

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   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z