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   ACUS01 KWNS 181633   
   SWODY1   
   SPC AC 181631   
      
   Day 1 Convective Outlook   
   NWS Storm Prediction Center Norman OK   
   1031 AM CST Thu Dec 18 2025   
      
   Valid 181630Z - 191200Z   
      
   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF   
   THE MISSISSIPPI/TENNESSEE/LOWER OHIO VALLEYS...AND PORTIONS OF   
   COASTAL NORTH CAROLINA...   
      
   ...SUMMARY...   
   Isolated strong to severe thunderstorms capable of producing   
   occasional damaging winds and perhaps a tornado or two may occur   
   through this evening across parts of the lower/mid Mississippi   
   Valley into the Tennessee Valley/Southeast, and late tonight across   
   portions of coastal North Carolina.   
      
   ...Tennessee Valley/Lower Ohio Valley into the Southeast...   
   A pronounced mid/upper-level shortwave trough with attendant 70-90   
   kt mid-level jet will advance quickly eastward today across the   
   Upper Midwest into the MS/OH/TN Valleys. An associated deep surface   
   low over northern MN this morning is forecast to continue developing   
   northeastward into Ontario/Quebec through tonight, with a trailing   
   cold front forecast to sweep east-southeastward over much of the   
   mid/lower MS Valley into the OH/TN Valleys and Southeast. Low-level   
   moisture return ahead of the cold front remains quite limited,   
   except for parts of MS/AL where low to mid 60s surface dewpoints are   
   beginning to spread inland. Even so, wind fields remain quite   
   favorable for thunderstorm organization, with ample low-level and   
   deep-layer shear present. Current expectations are for a low-topped   
   line of convection to further develop along the cold front through   
   this afternoon/evening. Although instability is expected to remain   
   minimal with northward extent into the OH/TN Valleys, there is still   
   potential for strong to severe gusts that will be convectively   
   enhanced beyond the already strong background gradient wind field.   
   Some chance for a tornado may also exist across parts of MS/AL where   
   greater instability/low-level moisture will reside. Given latest   
   observational and guidance trends, a Marginal Risk has been included   
   where the best potential for occasional strong to damaging winds is   
   apparent.   
      
   ...Coastal North Carolina...   
   Isolated strong to locally severe convection may occur late tonight   
   through early Friday morning as an increasingly negative-tilt   
   mid-level trough and a related robust strengthening of the   
   deep-layer wind field approach eastern NC. The gradual modification   
   and erosion of continental/cold air is a key uncertainty due to   
   persistent surface high pressure along the East Coast into western   
   Atlantic. Some guidance such as the 12Z NAM may be a bit too   
   aggressive regarding late-night near-surface-based destabilization.   
   Still, the main area of concern is for the immediate NC coastal   
   areas/Outer Banks, where somewhat greater airmass   
   modification/low-level moistening should occur amid strong low-level   
   and deep-layer shear. If surface-based thunderstorms can form and   
   spread northeastward across this area, they could pose a threat for   
   isolated severe/damaging winds and perhaps a tornado. But, it is   
   also possible that convectively enhanced wind gusts materialize   
   inland (including Piedmont areas) in the predawn hours, although   
   confidence in this occurring remains low.   
      
   ..Gleason/Weinman.. 12/18/2025   
      
   $$   
      
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