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Mesoscale Discussion 642
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   MESOSCALE DISCUSSION 0642
   NWS STORM PREDICTION CENTER NORMAN OK
   0755 PM CDT WED APR 27 2011
   
   AREAS AFFECTED...MUCH OF AL AND NORTHWEST/WEST-CENTRAL GA
   
   CONCERNING...TORNADO WATCH 235...
   
   VALID 280055Z - 280200Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 235 CONTINUES.
   
   PARTICULARLY DANGEROUS SITUATION /PDS/ TORNADO WATCH 235 CONTINUES
   UNTIL 03Z...WITH A CONTINUED HIGH-END RISK FOR STRONG/PERHAPS
   VIOLENT TORNADOES ESPECIALLY ACROSS A LARGE PART OF
   EAST-CENTRAL/SOUTH-CENTRAL AL INTO NORTHWEST GA. GIVEN A SCHEDULED
   03Z EXPIRATION OF TORNADO WATCH 235...EARLY INDICATIONS ARE THAT A
   REPLACEMENT TORNADO WATCH WILL LIKELY BE NEEDED. THIS REMAINS A
   POTENTIALLY LIFE-THREATENING SCENARIO.
   
   NOT SURPRISING GIVEN A NUMBER OF DESTRUCTIVE TORNADOES SINCE THIS
   AFTERNOON...THE 00Z OBSERVED BIRMINGHAM RAOB SAMPLED A CLASSIC
   STRONG TORNADO ENVIRONMENT/PARAMETER SPACE...HIGHLIGHTED BY HIGH
   BOUNDARY LAYER MOISTURE CONTENT AND VERY STRONG 0-1 KM SRH OF 450
   M2/S2 VIA A LONG CURVING HODOGRAPH WITHIN THE LOWEST 1-2 KM. WITH
   TIME...OBSERVATIONAL TRENDS/SHORT TERM GUIDANCE SUGGEST THE
   STRONGEST 1-2 KM FLOW WILL CONTINUE TO SHIFT EAST-NORTHEASTWARD
   ACROSS EASTERN AL INTO NORTHERN GA/THE SOUTHERN APPALACHIANS
   VICINITY. THERMODYNAMICALLY...THE BOUNDARY LAYER WILL BE VERY SLOW
   TO DECOUPLE AFTER DARK GIVEN THE HIGH MOISTURE CONTENT...AMID LOWER
   70S F SURFACE DEWPOINTS AND 16 G/KM MEAN MIXING RATIO PER THE 00Z
   BIRMINGHAM RAOB.
   
   OF NOTE...ONGOING TORNADIC SUPERCELLS ASIDE...SHORT TERM
   OBSERVATIONAL TRENDS IMPLY THAT ADDITIONAL STORMS/SUPERCELLS ARE
   LIKELY TO CONTINUE TO DEVELOP/INCREASE IN THE SHORT-TERM ACROSS
   SOUTH-CENTRAL/EAST-CENTRAL AL AMID A ZONE OF SHARPENING LOW LEVEL
   CONFLUENCE. THIS WOULD INCLUDE THE VICINITY OF MONTGOMERY AND NEARBY
   I-65/I-85 GENERAL VICINITIES. ACCORDINGLY...SUSTAINED/RELATIVELY
   DISCRETE TORNADIC SUPERCELLS...WITH CONTINUED STRONG/PERHAPS VIOLENT
   TORNADO POTENTIAL...ARE LIKELY TO PERSIST WITHIN A WSW-ENE ORIENTED
   BROAD CORRIDOR ACROSS A LARGE PART OF CENTRAL/PORTIONS OF SOUTHERN
   AL INTO NORTHWEST/WEST-CENTRAL GA THIS EVENING.
   
   ..GUYER.. 04/28/2011
   
   
   ATTN...WFO...FFC...BMX...HUN...MOB...
   
   LAT...LON   32158831 34098703 34828526 32308546 31298696 32158831 
   
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Page last modified: April 28, 2011
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