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   PID: Synchronet 3.21a-Linux master/123f2d28a Jul 12 2025 GCC 12.2.0   
   TID: SBBSecho 3.28-Linux master/123f2d28a Jul 12 2025 GCC 12.2.0   
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   ACUS01 KWNS 231947   
   SWODY1   
   SPC AC 231945   
      
   Day 1 Convective Outlook   
   NWS Storm Prediction Center Norman OK   
   0145 PM CST Tue Dec 23 2025   
      
   Valid 232000Z - 241200Z   
      
   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF   
   COASTAL CALIFORNIA...   
      
   ...SUMMARY...   
   An isolated threat for severe/damaging gusts and perhaps a brief   
   tornado may develop late tonight/early Wednesday morning across   
   parts of coastal California.   
      
   ...20Z Update...   
   Relatively minor adjustments to the general thunder forecast were   
   made based on the latest observations and model guidance. The   
   remainder of the forecast remains unchanged. See the previous   
   discussion for additional information.   
      
   ..Wendt.. 12/23/2025   
      
   .PREV DISCUSSION... /ISSUED 1020 AM CST Tue Dec 23 2025/   
      
   ...California...   
   Within large-scale upper troughing over the eastern Pacific, an   
   embedded mid-level shortwave trough will move quickly eastward and   
   approach the CA Coast late tonight/early Wednesday morning. A   
   corresponding strengthening and increase in the flow through much of   
   the troposphere is anticipated late in the period, with a surface   
   low also forecast to deepen along/near the coast of northern CA. A   
   cold front attendant to this surface low will sweep quickly   
   eastward, and should be approaching/onshore across parts of coastal   
   northern/central CA by 12Z early Wednesday morning. Current   
   expectations are for the thermodynamic profile to remain mostly   
   saturated, with poor lapse rates generally limiting instability.   
   Even so, it appears that a gradual increase in low-level moisture   
   ahead of the cold front and slightly cooling mid-level temperatures   
   with the approach of the shortwave trough may support weak but   
   sufficient MUCAPE for an organized band of low-topped thunderstorms   
   late tonight.   
      
   Most guidance suggests this convection will not impact parts of   
   coastal CA until after 24/06Z, and there is still significant   
   uncertainty whether enough boundary-layer instability will be   
   present to support surface-based convection. There is also a signal   
   for pre-frontal convection in the low-level warm advection regime   
   across parts of central into coastal southern CA. Given the strength   
   of the low/mid-level flow forecast, and related strong   
   low-level/deep-layer shear, it appears that convectively enhanced   
   winds may be capable of reaching severe levels and producing damage   
   on an isolated basis even if instability remains minimal. A brief   
   tornado may also occur if convection can become truly surface based,   
   as effective SRH will be enhanced by a 50-70 kt southerly low-level   
   jet. Based on latest guidance trends, the Marginal Risk has been   
   expanded southward along the coast to include more of   
   central/southern CA. This isolated severe threat is expected to   
   continue beyond 12Z Wednesday into the Day 2 period.   
      
   $$   
      
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   --- SBBSecho 3.28-Linux   
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