MESOSCALE DISCUSSION 0451
   NWS STORM PREDICTION CENTER NORMAN OK
   1205 PM CDT MON APR 28 2014

   AREAS AFFECTED...PORTIONS NERN LA...WRN/NRN MS...NWRN AL...SRN
   MIDDLE TN.

   CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 

   VALID 281705Z - 281900Z

   PROBABILITY OF WATCH ISSUANCE...95 PERCENT

   SUMMARY...TORNADO WATCH IS HIGHLY PROBABLE WITHIN NEXT HOUR ACROSS
   DISCUSSION AREA.  SUPERCELLS ARE EXPECTED TO DEVELOP IN BKN/SW-NE
   BAND AND INTENSIFY THROUGH AFTN WITH A FEW SIGNIFICANT/LONG-TRACK
   TORNADOES POSSIBLE.

   DISCUSSION...EARLIER CONVECTION HAS LEFT
   OUTFLOW/DIFFERENTIAL-HEATING BOUNDARY ALIGNED SW-NE ACROSS
   DISCUSSION AREA...BECOMING MORE DIFFUSE WITH SWWD EXTENT AT SFC. 
   MEANWHILE VIS IMAGERY SHOWS EXPANDING POCKETS OF RELATIVELY
   CLOUD-FREE AREAS THAT WILL FOSTER SUSTAINED PERIOD OF INSOLATION AND
   QUICK SBCINH REMOVAL.  MODIFIED RAOBS AND FCST SOUNDINGS OVER THIS
   CORRIDOR SUGGEST 1500-2500 J/KG MLCAPE WILL BUILD NEWD.  IN THIS
   ENVIRONMENT...TSTMS ALREADY ARE DEVELOPING OVER NERN LA INVOF
   MLU...AND IF NOT ALREADY SFC-BASED...MAY BECOME SO SHORTLY. 
   ADDITIONAL CONVECTION IS LIKELY TO FORM NEWD ACROSS MS INTO SRN MID
   TN AND NWRN AL AS AIR MASS THERE DESTABILIZES IN NEXT 2-3 HOURS. 
   DEEP-LAYER AND LOW-LEVEL SHEAR EACH ARE FAVORABLE AND WILL REMAIN
   SO...WITH 50-70 KT EFFECTIVE SHEAR MAGNITUDES.  EFFECTIVE SRH SHOULD
   INCREASE THROUGH AFTN TO AROUND 300 J/KG...AND VWP ALREADY SHOW
   300-500 J/KG OF 0-3 KM SRH OVER NERN MS.

   ..EDWARDS/THOMPSON.. 04/28/2014


   ATTN...WFO...OHX...BMX...HUN...MEG...JAN...SHV...

   LAT...LON   31839293 33109109 33899025 34938907 35578817 35738717
               35738680 35548640 35148622 34618635 33918718 32908827
               32118944 31619029 31419147 31549218 31839293