MESOSCALE DISCUSSION 0582
   NWS STORM PREDICTION CENTER NORMAN OK
   1105 PM CDT MON APR 25 2011
   
   AREAS AFFECTED...PORTIONS EXTREME SERN IL...EXTREME SERN
   MO...EXTREME SWRN INDIANA...WRN KY...WRN-MIDDLE TN...NERN LA...SERN
   AR...NRN/WRN MS...NWRN AL.
   
   CONCERNING...TORNADO WATCH 206...207...
   
   VALID 260405Z - 260600Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 206...207...CONTINUES.
   
   SQUALL LINE...WITH EMBEDDED BOW/LEWP FEATURES AND LEADING-EDGE
   VORTICES POSSIBLE...WILL POSE PRIMARY DAMAGING WIND RISK AND
   POTENTIAL FOR A FEW QLCS TORNADOES AS IT CONTINUES EWD ACROSS LOWER
   OH RIVER REGION AND ESPECIALLY WRN TN/NWRN MS.  WW 206 IS SCHEDULED
   TO EXPIRE AT 05Z...AND ADDITIONAL WW MAY BE NEEDED ACROSS MORE OF
   TN/KY/NRN MS AND PERHAPS NWRN AL BEFORE THAT TIME.
   
   AVAILABLE LOW-LEVEL MOISTURE WILL INCREASE WITH SWD EXTENT AHEAD OF
   THIS ACTIVITY...COMBINING WITH FORCED ASCENT ALONG LEADING EDGE OF
   COLD POOL TO SUSTAIN MCS FOR AT LEAST ANOTHER COUPLE OF HOURS. 
   60-70 KT LLJ ALSO WILL AID IN MOISTURE ADVECTION/TRANSPORT ABOVE
   SFC...IN NARROW CORRIDOR AHEAD OF THIS COMPLEX.  MAIN UNCERTAINTY
   ATTM IS HOW FAR E DAMAGING WIND POTENTIAL WILL PERSIST ACROSS THIS
   REGION GIVEN STRENGTHENING NEAR-SFC STABILITY WITH TIME...DUE TO
   DIABATIC COOLING...AND WITH EWD EXTENT...DUE TO LOWER-THETAE SFC
   TRAJECTORIES.  MODIFIED RAOBS AND RUC SOUNDINGS SUGGEST NEAR-SFC
   STABLE LAYER MAY BE SUFFICIENTLY SHALLOW TO ALLOW DAMAGING GUSTS TO
   PENETRATE TO SFC ACROSS MUCH OF NRN MS AND PERHAPS MIDDLE TN.
   OBSERVED GUSTS AT OBSERVATION SITES HAVE BEEN MOSTLY
   SUBSEVERE...EXCEPT ONE MEASURED AT 50 KT AT BYH AT 337Z AND HIGHER
   ESTIMATED GUSTS ACCORDING TO SPOTTER REPORTS.  DEEP-LAYER WIND
   PROFILES WILL REMAIN QUITE FAVORABLE FOR DAMAGING WIND AND...WHERE
   SUPPORTIVE MESOCIRCULATIONS CAN DEVELOP ON STORM SCALE...TORNADO
   POTENTIAL.
   
   ..EDWARDS.. 04/26/2011
   
   
   ATTN...WFO...LMK...OHX...BMX...HUN...PAH...MEG...JAN...LZK...
   SHV...
   
   LAT...LON   33079259 33219190 33589142 34179062 34639025 35498975
               36028975 37038905 37608870 38118834 38028703 37438654
               36538662 35378703 34158790 33188896 32539132 33079259