354  
ACUS03 KWNS 230727  
SWODY3  
SPC AC 230726  
 
DAY 3 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0226 AM CDT WED SEP 23 2020  
 
VALID 251200Z - 261200Z  
   
..NO SEVERE THUNDERSTORM AREAS FORECAST
 
 
   
..SUMMARY
 
 
THE POTENTIAL FOR ORGANIZED SEVERE THUNDERSTORMS ON FRIDAY ACROSS  
PARTS OF THE UPPER MIDWEST APPEARS TOO UNCERTAIN TO INCLUDE ANY RISK  
AREAS AT THIS TIME.  
   
..UPPER MIDWEST
 
 
A STRONG WESTERLY MID/UPPER-LEVEL JET IS FORECAST TO PERSIST ON  
FRIDAY ACROSS MUCH OF THE PACIFIC NORTHWEST TO THE NORTHERN ROCKIES  
AND NORTH-CENTRAL STATES. A SHORTWAVE TROUGH EMBEDDED WITHIN THIS  
FLOW REGIME SHOULD MOVE EASTWARD ACROSS THE UPPER MIDWEST THROUGH  
THE PERIOD. AT THE SURFACE, A COLD FRONT WILL LIKEWISE SWEEP  
EASTWARD ACROSS THIS REGION, WITH A MODEST INCREASE IN LOW-LEVEL  
MOISTURE OCCURRING AHEAD OF THE FRONT ACROSS PARTS OF EASTERN MN  
INTO WESTERN WI AND VICINITY. AT THIS POINT, MOST GUIDANCE SUGGESTS  
THAT WARM MID-LEVEL TEMPERATURES PRECEDING THE SHORTWAVE TROUGH WILL  
KEEP THE WARM SECTOR CAPPED THROUGH THE DAY. STILL, THERE IS A  
NON-ZERO CHANCE THAT NEAR-SURFACE-BASED STORMS COULD FORM ALONG OR  
JUST AHEAD OF THE FRONT ACROSS PARTS OF EAST-CENTRAL MN INTO  
NORTHWESTERN WI BY FRIDAY EVENING. IF THIS OCCURS, THEN SEVERE  
THUNDERSTORMS APPEAR POSSIBLE GIVEN THE FORECAST COMBINATION OF WEAK  
INSTABILITY WITH STRONG DEEP-LAYER SHEAR. HOWEVER, THE MORE PROBABLE  
SCENARIO IS FOR MAINLY ELEVATED STORMS TO FORM NORTH OF THE WARM  
SECTOR FRIDAY EVENING/NIGHT IN A LOW-LEVEL WARM ADVECTION REGIME,  
WITH A MINIMAL SEVERE RISK FARTHER SOUTH. GIVEN THESE UNCERTAINTIES  
AND MODEL DIFFERENCES, HAVE OPTED TO DEFER POSSIBLE INCLUSION OF LOW  
SEVERE PROBABILITIES ACROSS THIS REGION TO A LATER OUTLOOK.  
   
..SOUTHEAST
 
 
ISOLATED TO SCATTERED THUNDERSTORMS MAY OCCUR ACROSS A BROAD PORTION  
OF THE SOUTHEAST ON FRIDAY AS A WEAK, POSITIVELY TILTED SHORTWAVE  
TROUGH MOVES EASTWARD OVER THIS REGION. ALTHOUGH MID-LEVEL  
SOUTHWESTERLY FLOW SHOULD BE MODESTLY ENHANCED, THE LACK OF ANY  
DISCERNIBLE SURFACE LOW, POOR MID-LEVEL LAPSE RATES, AND WEAK  
INSTABILITY ALL SUGGEST THAT ANY ORGANIZED SEVERE THUNDERSTORM RISK  
SHOULD REMAIN LOW.  
 
..GLEASON.. 09/23/2020  
 

 
 
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