675  
ACUS11 KWNS 071012  
SWOMCD  
SPC MCD 071011  
MSZ000-LAZ000-071245-  
 
MESOSCALE DISCUSSION 0055  
NWS STORM PREDICTION CENTER NORMAN OK  
0411 AM CST WED FEB 07 2018  
 
AREAS AFFECTED...PORTIONS OF CENTRAL LA TO SOUTH-CENTRAL MS  
 
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY  
 
VALID 071011Z - 071245Z  
 
PROBABILITY OF WATCH ISSUANCE...20 PERCENT  
 
SUMMARY...RISKS FOR DAMAGING, NEAR-SEVERE GUSTS AND A TORNADO EXIST  
PRIMARILY FROM A BAND OF FRONTAL THUNDERSTORMS CROSSING THE  
DISCUSSION AREA. THIS THREAT SHOULD DIMINISH WITH TIME THROUGH  
MIDMORNING, THOUGH THUNDERSTORM COVERAGE MAY TEMPORARILY INCREASE.  
 
DISCUSSION...THUNDERSTORMS HAVE BEEN INCREASING IN COVERAGE AND  
INTENSITY THE PAST 1-2 HOURS ALONG A COLD FRONT THAT WAS ANALYZED  
FROM EASTERN KY SOUTHWESTWARD ACROSS CENTRAL PORTIONS OF MS AND LA.  
AHEAD OF THE FRONT, A BAND OF MOSTLY ELEVATED THUNDERSTORMS AND  
RELATED BOUNDARY OF PRECIP-COOLED AIR WAS DRAWN FROM NEAR BHM TO MEI  
THEN ACROSS THE MISSISSIPPI RIVER JUST NORTH OF HEZ. MINOR  
NORTHWARD MOVEMENT OF THE WESTERN PART OF THE BOUNDARY IS POSSIBLE  
BEFORE BEING OVERTAKEN BY THE COLD FRONT AND RELATED CONVECTION. A  
DIFFUSE MARINE/WARM FRONT WAS ANALYZED ACROSS SOUTHEASTERN MS AND  
SOUTHWESTERN AL, AND SHOULD MOVE SLOWLY NORTHEASTWARD THROUGH THE  
REMAINDER OF THE MORNING. SOUTH OF ALL THOSE BOUNDARIES, AND TO THE  
EXTENT CONVECTIVE MODE DOES NOT BECOME TOO LINEAR, THE WARM-SECTOR  
ENVIRONMENT FAVORS MESSY SUPERCELL STRUCTURES, WITH MODIFIED RAOBS  
AND FORECAST SOUNDINGS SUGGESTING MLCAPE 500-1000 J/KG (AMIDST 60S F  
SURFACE DEW POINTS), AROUND 150-250 J/KG EFFECTIVE SRH, AND 45-55-KT  
EFFECTIVE-SHEAR MAGNITUDES.  
 
HOWEVER, WITH EACH PASSING HOUR, THE NEAR-SURFACE WINDS ARE EXPECTED  
TO VEER MORE OVER THE REGION AS THE SURFACE LOW ATTACHED TO THE COLD  
FRONT EJECTS FARTHER NORTHEASTWARD AWAY FROM THE AREA, INTO THE  
CENTRAL APPALACHIANS. THE STRONGEST PART OF THE LLJ, ALREADY EAST  
OF THE AREA, WILL FOLLOW. THAT VEERING NEAR-SURFACE AND REDUCTION  
OF WINDS IN THE LLJ LAYER SHOULD REDUCE LOW-LEVEL SHEAR AND  
CONTRIBUTE TO PROGRESSIVELY MORE SOLIDLY LINEAR CONVECTIVE MODE.  
HOWEVER, IN THE MEANTIME, THE THREAT FOR A BRIEF TORNADO OR LOCALLY  
DAMAGING GUSTS MAY CONTINUE.  
 
..EDWARDS.. 02/07/2018  
   
..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT
 
 
ATTN...WFO...JAN...LIX...LCH...SHV...  
 
LAT...LON 30689332 31589186 31899097 32168948 31398979 30909047  
30569218 30689332  
 
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