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   ACUS01 KWNS 240554   
   SWODY1   
   SPC AC 240553   
      
   Day 1 Convective Outlook   
   NWS Storm Prediction Center Norman OK   
   1153 PM CST Tue Dec 23 2025   
      
   Valid 241200Z - 251200Z   
      
   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS COASTAL   
   CALIFORNIA AND THE CENTRAL VALLEY...   
      
   ...SUMMARY...   
   Thunderstorms with marginally severe wind gusts, small hail and   
   potentially a brief tornado will be possible from Wednesday into   
   Wednesday night along parts of the California coast, and inland   
   across the San Joaquin Valley.   
      
   ... Synopsis ...   
      
   A high-amplitude midlevel pattern will persist on Wednesday,   
   characterized by a deep trough across the eastern Pacific and a   
   building ridge across the Plains. This pattern will maintain a broad   
   belt of intense cyclonic flow across California into the Interior   
   West.   
      
   Throughout the day, an initial shortwave trough will continue   
   lifting northeast from the eastern Pacific into the Pacific   
   Northwest, while the attendant surface low lifts more northward   
   along the coast toward Washington. Late on Wednesday a second, more   
   potent trough will approach central and northern California --   
   primarily after dark. This setup will facilitate a prolonged period   
   rain and embedded thunderstorms across California and portions of   
   the Interior West into Thursday.   
      
   ... California Coast ...   
      
   Strong ascent and strengthening onshore flow will aid in modest   
   destabilization Wednesday morning ahead of a surface cold front. An   
   ongoing band of convection is expected across the central and   
   southern coastal areas associated with the strongly forced ascent   
   along the advancing cold front. Given the presence of a strong   
   low-level jet (locally exceeding 50 knots at 1 km AGL), there is a   
   risk that these strong winds will mix to the surface within the   
   strongest convection resulting in damaging wind gusts. Forecast   
   soundings across the area do maintain some low-level curvature ahead   
   of the convective line, such that any convective element able to   
   interact with true surface-based buoyancy would have the potential   
   for a brief tornado.   
      
   In the wake of the morning convection, a secondary surface low will   
   intensify during the afternoon and overnight as it approaches the   
   northern California coast. This will likely trigger another round or   
   two of broken, low-topped convection along a second cold front.   
   Despite weaker instability than with the morning convection, the   
   strength of the wind fields would suggest an ongoing risk for   
   isolated wind damage as this convection moves inland.   
      
   ... Central Valley ...   
      
   Cold midlevel temperatures and increasing height falls will   
   overspread surface dewpoints in the 40s to perhaps low 50s. Although   
   buoyancy will remain modest (MUCAPE at or below 500 J/kg), the   
   presence of a powerful midlevel jet in excess of 100 knots will   
   support long hodographs. This combination of modest instability and   
   large/long hodographs may support a threat for semi-organized   
   convection, including some potential for supercells. The strongest   
   storms will be capable of producing damaging gusts, hail, and a   
   brief tornado before the convection shifts east into the higher   
   terrain and weakens.   
      
   ..Marsh/Squitieri.. 12/24/2025   
      
   $$   
      
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