921  
ACUS01 KWNS 041235  
SWODY1  
SPC AC 041234  
 
DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0734 AM CDT SAT NOV 04 2017  
 
VALID 041300Z - 051200Z  
   
..NO SEVERE THUNDERSTORM AREAS FORECAST
 
 
   
..SUMMARY
 
 
THE RISK FOR SEVERE STORMS APPEARS MINIMAL ACROSS THE U.S. TODAY AND  
TONIGHT.  
   
..SYNOPSIS
 
 
MID/UPPER WINDS BEGIN THE PERIOD WITH A STRONGLY ZONAL COMPONENT  
ACROSS MOST OF THE CONTIGUOUS U.S. HOWEVER, THE PATTERN WILL TREND  
MORE CYCLONIC OVER THE WESTERN U.S. AND THE CENTRAL/NORTHERN PLAINS  
THROUGH 12Z, AS A SERIES OF SHORTWAVE TROUGHS CONTRIBUTES TO GENERAL  
HEIGHT FALLS.  
 
AT THE SURFACE, 11Z ANALYSIS SHOWED THREE MAIN FRONTAL ZONES EAST OF  
THE ROCKIES...  
1. A MARINE/WARM FRONT WITH HIGH-THETA-E GULF BOUNDARY LAYER TO ITS  
SOUTH, IN AN ARC NEAR DRT-TXK-BIX. MOST OF THIS BOUNDARY WILL  
PROCEED NORTHWARD, BECOME MORE DIFFUSE, AND ULTIMATELY MERGE WITH  
THE NEXT ONE.  
2. A SYNOPTIC FRONT, MOSTLY WARM IN CHARACTER, FROM A LOW OVER THE  
TEXAS PANHANDLE TO ANOTHER OVER NORTH-CENTRAL MO, THEN EAST-  
SOUTHEASTWARD ACROSS EASTERN KY. THE FRONTAL SEGMENT GENERALLY EAST  
OF THE MISSISSIPPI RIVER SHOULD SHIFT NORTHEASTWARD AND BECOME  
DIFFUSE AMIDST BROAD A PLUME OF LOW-LEVEL WARM ADVECTION.  
3. AN ARCTIC COLD FRONT, ANALYZED OVER EASTERN MT, AND FORECAST TO  
SWEEP EASTWARD/SOUTHEASTWARD ACROSS MUCH OF THE NORTHERN/CENTRAL  
PLAINS THROUGH THE PERIOD. BY 12Z, THIS BOUNDARY SHOULD EXTEND FROM  
A DEEPENING CYCLONE OVER NORTHWESTERN ON ACROSS LAKE SUPERIOR,  
SOUTHEASTERN MN, WESTERN IA, NORTHERN/WEST-CENTRAL KS, AND  
NORTHEASTERN CO. THIS FRONT WILL MERGE WITH #2 EARLY IN THE DAY-2  
PERIOD AND CONTRIBUTE TO THAT SEVERE-STORM THREAT.  
   
..GENERAL-THUNDERSTORM AREA
 
 
A BROAD LOW-LEVEL WARM-ADVECTION REGIME, GENERALLY POSITIONED UNDER  
WEAK BUT SUFFICIENT LAPSE RATES ALOFT, WILL COMBINE WITH AT LEAST  
MARGINALLY FAVORABLE LOW-LEVEL MOISTURE, TO SUPPORT THE POTENTIAL  
FOR THUNDERSTORMS IN THE DENOTED AREA THROUGH THE PERIOD. POCKETS  
OF SURFACE DIABATIC HEATING WILL BOOST INSTABILITY AND WEAKEN MLCINH  
TODAY, IN THAT PART OF THIS OUTLOOK EQUATORWARD OF THE MIDDLE FRONT  
(#2).  
 
COVERAGE SHOULD REMAIN ISOLATED OVERALL, EXCEPT FOR WIDELY SCATTERED  
TO SCATTERED THUNDERSTORMS POSSIBLE OVERNIGHT ACROSS PARTS OF IN/OH.  
THAT AREA WILL RESIDE UNDER THE LEADING FRINGE OF A SWATH OF  
FAVORABLE LOW-LEVEL WARM ADVECTION AND MOISTURE TRANSPORT, AMIDST A  
BROAD/40-50-KT LLJ. ISENTROPIC LIFT OF PARCELS TO LFC SHOULD OCCUR  
WITH ELEVATED MUCAPE OF 200-700 J/KG, AMIDST 30-40 KT EFFECTIVE-  
SHEAR MAGNITUDES. THIS MAY SUPPORT SUBSEVERE HAIL WITH A FEW CELLS;  
HOWEVER, THE RISK FOR SEVERE HAIL APPEARS TOO CONDITIONAL AND  
ISOLATED FOR CATEGORICAL-LEVEL PROBABILITIES AT THIS TIME.  
 
..EDWARDS.. 11/04/2017  
 

 
 
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