345  
ACUS01 KWNS 041629  
SWODY1  
SPC AC 041627  
 
DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
1027 AM CST MON DEC 04 2017  
 
VALID 041630Z - 051200Z  
 
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS  
AFTERNOON/EVENING FROM EASTERN OK AND NORTHWESTERN AR TO  
NORTHEASTERN MO...  
 
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON  
THROUGH TONIGHT FROM SOUTHEASTERN IA/NORTHWESTERN IL TO EXTREME  
NORTHEASTERN TX AND AR...  
   
..SUMMARY
 
 
ISOLATED STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED ACROSS EASTERN  
OKLAHOMA AND THE ARK-LA-TEX REGION INTO MISSOURI AND SOUTHEAST  
IOWA/NORTHWEST ILLINOIS LATE THIS AFTERNOON INTO TONIGHT.  
   
..SYNOPSIS
 
 
A SURFACE CYCLONE IN SOUTHWEST MN THIS MORNING WILL MOVE TOWARD LAKE  
SUPERIOR BY TONIGHT, WITH RAPID DEEPENING EXPECTED IN RESPONSE TO  
STRONG DEEP-LAYER FORCING FOR ASCENT WITHIN THE LEFT EXIT REGION OF  
A 130 KT UPPER JET STREAK. AN ASSOCIATED SURFACE COLD FRONT WILL  
SURGE SOUTHEASTWARD IN THE WAKE OF THE CYCLONE AND CROSS THE MID MS  
VALLEY AND SOUTHERN PLAINS BY THE END OF THIS FORECAST PERIOD. IN  
ADVANCE OF THE COLD FRONT, A NARROW MOIST SECTOR WITH BOUNDARY-LAYER  
DEWPOINTS IN THE MID 50S INTO IA AND MID-UPPER 60S IN TX, WILL  
CONTINUE TO SPREAD NORTHEASTWARD THROUGH THE DAY. THOUGH SURFACE  
HEATING WILL BE TEMPERED BY WIDESPREAD CLOUDS, THE LOW-LEVEL  
MOISTURE AND REMNANT STEEP MIDLEVEL LAPSE RATES WILL SUPPORT AT  
LEAST WEAK SURFACE-BASED BUOYANCY AS FAR NORTHEAST AS PARTS OF  
IA/IL.  
   
..MID MS VALLEY TO THE OZARKS THROUGH TONIGHT
 
 
THUNDERSTORM DEVELOPMENT IS EXPECTED IN A BAND ALONG THE COLD FRONT  
FROM MID-LATE AFTERNOON (21-23Z). IT APPEARS THERE WILL BE A 2-4  
HOUR WINDOW OF OPPORTUNITY FOR DAMAGING WINDS (AND PERHAPS AN  
ISOLATED TORNADO) THIS EVENING AS FAR NORTHEAST AS SOUTHEAST IA AND  
NORTHWEST IL, GIVEN BUOYANCY ROOTED AT THE SURFACE AND 50-60 KT FLOW  
JUST ABOVE THE SURFACE. STRONG DEEP-LAYER SHEAR MAY SUPPORT  
EMBEDDED SUPERCELLS WITHIN THE LINE FOR A FEW HOURS THIS EVENING.  
THE FRONTAL CONVECTION WILL MAINTAIN INTENSITY LONGER FROM EASTERN  
OK INTO AR, WHERE MID 60S DEWPOINTS WILL DRIVE AT LEAST WEAK  
BUOYANCY INTO TONIGHT. HOWEVER, THE CONVECTION WILL BECOME MORE  
ANAFRONTAL WITH TIME AND LOW-LEVEL FLOW WILL VEER/WEAKEN, WHICH WILL  
LIMIT THE SOUTHWESTWARD EXTENT OF ANY SEVERE-STORM THREAT.  
 
..THOMPSON/BUNTING.. 12/04/2017  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab SPC Page Main Text Page