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Mesoscale Discussion 438
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   MESOSCALE DISCUSSION 0438
   NWS STORM PREDICTION CENTER NORMAN OK
   0130 PM CDT FRI APR 15 2011
   
   AREAS AFFECTED...PORTIONS MS...CENTRAL-ERN LA...AL...EXTREME WRN GA.
   
   CONCERNING...TORNADO WATCH 140...141...
   
   VALID 151830Z - 152030Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 140...141...CONTINUES.
   
   CONTINUE W 141.  REPLACEMENT WW FOR 140 IS LIKELY BEFORE SCHEDULED
   20Z EXPIRATION...BECAUSE SVR THREAT WILL PERSIST WELL BEYOND THAT
   TIME AND PRIOR TO COLD FROPA.
   
   18Z SFC MESOANALYSIS SHOWED COLD FRONT CONTINUING TO MOVE EWD ACROSS
   NERN...CENTRAL AND SWRN LA...WITH WARM FRONT ANALYZED ROUGHLY 30 NNE
   TCL...TCL...GZH...NSE AND LIFTING NEWD ACROSS W-CENTRAL/S-CENTRAL
   AL.  PRE COLD-FRONTAL CONFLUENCE LINE IS PIVOTING EWD ACROSS
   SWRN/CENTRAL MS WHILE DRIFTING EWD ACROSS SERN LA.  AS THESE
   PROCESSES CONTINUES...FAVORABLY BUOYANT AND STRONGLY HEATED AIR
   MASS...CHARACTERIZED BY MLCAPE 1000-2000 J/KG...WILL OVERSPREAD
   PROGRESSIVELY MORE OF CENTRAL/SRN AND EVENTUALLY ERN AL...THROUGH
   LATE AFTERNOON.  NRN FRINGE OF STRONGEST HEATING IS EVIDENT IN SFC
   DATA AND VIS IMAGERY ROUGHLY ALONG JAN-EET LINE...AND HAS MOVED N OF
   MEI.  STORMS WITHIN AND JUST N OF THAT BOUNDARY MAY ENCOUNTER
   ENHANCED LOW-LEVEL VORTICITY/ASCENT.  THIS INCLUDES LONG-LIVED
   SUPERCELL NOW MOVING TOWARD PORTIONS SUMTER/GREENE/HALE/TUSCALOOSA
   COUNTIES AL THAT PRODUCED DAMAGING TORNADO IN JAN AREA AROUND
   16Z...AND MORE RECENTLY...REPORT OF LARGE TORNADO IN KEMPER COUNTY
   AT 1820Z.  UPSHEAR SUPERCELLS S AND SW JAN ALSO MAY INTERACT WITH
   THAT BOUNDARY.  CELLS OVER SERN MS AND SRN AL MAY ENCOUNTER WARM
   FRONT...WHERE LOW-LEVEL BACKING/VORTICITY/HODOGRAPHS WILL BE
   RELATIVELY MAXIMIZED.  BOTH REGIMES MAY SUPPORT CORRIDORS OF LOCALLY
   ENHANCED TORNADO POTENTIAL...WITH EFFECTIVE SRH REACHING 500 J/KG. 
   HOWEVER...STG LOW-MIDLEVEL SPEED SHEAR WILL SUPPORT SUPERCELL THREAT
   EVEN AS FAR W AS S-CENTRAL LA.
   
   SVR POTENTIAL MAY EXTEND INTO PORTIONS WRN GA DURING NEXT 2-3 HOURS
   WITH CELLS WELL NE OF SFC WARM FRONT...BUT IN REGIME OF ELEVATED WAA
   AND STRENGTHENING BUOYANCY/SHEAR ALOFT...SUPPORTING OCNL HAIL. 
   BETTER-ORGANIZED THREAT THERE IS NOT EXPECTED UNTIL LATE AFTERNOON
   INTO EVENING.
   
   ..EDWARDS.. 04/15/2011
   
   
   ATTN...WFO...FFC...TAE...BMX...HUN...MOB...MEG...JAN...LIX...
   LCH...SHV...
   
   LAT...LON   31109248 32009153 33558978 34078871 34338761 34908581
               33858503 32708523 31548577 31108703 30958751 30488839
               30459014 30569233 31109248 
   
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Page last modified: April 15, 2011
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