SPC AC 100507

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1207 AM CDT Thu Aug 10 2023

   Valid 101200Z - 111200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   THE NORTHERN PLAINS...AND OVER PARTS OF THE CAROLINAS INTO FAR
   SOUTHEAST VIRGINIA...

   ...SUMMARY...
   Strong to severe thunderstorms are possible across parts of the
   northern Plains, and from the Tennessee Valley to the Mid-Atlantic
   on Thursday.

   ...Southeast to Mid-Atlantic Coast...

   A midlevel shortwave trough will be oriented over the OH/TN Valley
   vicinity this morning, and pivot east/northeast through the day,
   moving offshore the Mid-Atlantic coast by late evening. A belt of
   40-60 kt 500 mb west/southwest flow will overspread the region,
   supporting organized convection, as effective shear magnitudes
   approach 30-40 kt. An MCS will likely be ongoing over the southern
   Appalachians this morning, and may deteriorate as it shifts east
   through midday. A second area of thunderstorms may then develop
   ahead of an eastward-progressing surface low over NC. A moist
   airmass, with dewpoints generally in the upper 60s to mid 70s F will
   support moderate to strong destabilization by afternoon. Bowing
   clusters and perhaps a couple of discrete cells are expected across
   parts of SC/NC toward coastal SE VA. Isolated to scattered damaging
   gusts and a couple of tornadoes are possible. 

   Further to the west, scattered thunderstorms are expected to develop
   from northeast MS into AL/GA along residual outflow from prior
   convection. While vertical shear will be somewhat weaker across this
   area, moderate to strong instability and a very moist airmass will
   support clusters of storms capable of isolated damaging gusts.

   ...Northern Plains vicinity...

   The upper ridge over the region will shift east toward the upper
   Great Lakes today as a weak midlevel shortwave impulse migrates east
   from the northern Rockies to the Upper MS Valley. At the surface, a
   cold front will develop eastward across the Dakotas and NE during
   the afternoon/evening. Modest boundary-layer moisture amid steep
   midlevel lapse rates will foster MLCAPE around 1000-2000 J/kg.
   Modestly veering wind profiles, and around 30 kt 0-6 km shear, will
   support a mix of semi-discrete cells and clusters. A deeply mixed
   boundary-layer will support strong/severe gusts while
   elongated/straight hodographs above 2-3 km amid steep midlevel lapse
   rates suggest large hail also will be possible. 

   ...Southern New England...

   A weak surface low and cold front will shift east across New England
   during the afternoon/evening. A seasonally moist airmass will be in
   place. However, poor midlevel lapse rates and muted heating due to
   cloud cover will largely limit severe potential, though a few strong
   gusts are possible with storms across Upstate NY eastward. The best
   chance for a severe storm appears to be closer to coastal southern
   New England where a better overlap of deeper boundary-layer moisture
   and stronger surface heating will occur. A few strong gusts and a
   tornado will be possible within this environment.

   ..Leitman/Moore.. 08/10/2023

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