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Mesoscale Discussion 640
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   MESOSCALE DISCUSSION 0640
   NWS STORM PREDICTION CENTER NORMAN OK
   0639 PM CDT WED APR 27 2011
   
   AREAS AFFECTED...MUCH OF AL/NORTHWEST GA
   
   CONCERNING...TORNADO WATCH 235...
   
   VALID 272339Z - 280045Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 235 CONTINUES.
   
   PARTICULARLY DANGEROUS SITUATION /PDS/ TORNADO WATCH 235 CONTINUES
   UNTIL 03Z.
   
   A HIGH-END TORNADO OUTBREAK WILL CONTINUE INTO THIS EVENING ACROSS A
   LARGE PART OF CENTRAL/NORTHEAST AL AND NORTHWEST GA. THIS IS AN
   EXTREMELY DANGEROUS AND LIFE-THREATENING SITUATION! CITIES AND AREAS
   AT GREATEST RISK INCLUDE BIRMINGHAM...THE I-59 CORRIDOR OF
   WESTERN/NORTHEAST AL...I-65 ACROSS NORTHERN/CENTRAL AL...AND I-20.
   
   23Z SURFACE ANALYSIS CONTINUES TO REFLECT A HIGHLY FAVORABLE
   ENVIRONMENT FOR TORNADIC SUPERCELLS...WITH RELATIVELY STRONG
   SOUTHERLY LOW LEVEL WINDS COINCIDENT WITH NEAR 70F SURFACE DEWPOINTS
   ESPECIALLY WITHIN AN AXIS FROM EAST-CENTRAL MS INTO WEST-CENTRAL TO
   NORTHEAST AL/NORTHWEST GA. IN PROXIMITY TO DESTRUCTIVE TORNADIC
   SUPERCELL NEAR/NORTH OF BIRMINGHAM...WSR-88D VWP DATA NOW REFLECTS
   0-1 KM SRH IN EXCESS OF 600 M2/S2. A SEMI-DISCRETE/SUSTAINED
   SUPERCELLULAR MODE...COINCIDENT WITH THE GREATEST INGREDIENTS FOR
   STRONG/VIOLENT TORNADOES...IS EXPECTED TO REMAIN ACROSS WEST-CENTRAL
   TO NORTHEAST/EAST-CENTRAL AL AND NORTHWEST GA THROUGH EARLY EVENING.
   A CORRIDOR OF ROUGHLY 50 MILES EITHER SIDE OF I-59...AS WELL AS THE
   GENERAL VICINITY OF I-20...REMAINS OF PARTICULARLY HIGH CONCERN FOR
   LONG-LIVED/DESTRUCTIVE TORNADIC SUPERCELLS.
   
   ANOTHER RELATIVELY CONCENTRATED AREA OF HIGH SHORT-TERM CONCERN WILL
   REMAIN ACROSS FAR NORTHERN AL IN VICINITY OF A RECOVERING OUTFLOW
   BOUNDARY...WHILE STORMS ALONG THE EASTWARD-ADVANCING PRE-FRONTAL
   TROUGH/DRYLINE OTHERWISE INCREASE AND GROW UPSCALE/MERGE WITH
   LEADING SEMI-DISCRETE STORMS. THIS MORE LINEAR EVOLUTION WILL LIKELY
   TEMPER THE HIGH-END TORNADO POTENTIAL WITH TIME ACROSS NORTHERN
   AL...BUT THE RISK FOR DAMAGING WINDS/ISOLATED TORNADOES WILL
   NONETHELESS PERSIST THIS EVENING.
   
   ..GUYER.. 04/27/2011
   
   
   ATTN...WFO...FFC...BMX...HUN...MOB...
   
   LAT...LON   31558832 33758809 34798689 34548438 31988674 31558832 
   
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