MESOSCALE DISCUSSION 0681
   NWS STORM PREDICTION CENTER NORMAN OK
   1040 PM CDT SAT MAY 02 2009
   
   AREAS AFFECTED...CNTRL AL...CNTRL MS...NRN LA...SRN AR...SERN
   OK...NCNTRL/NERN TX
   
   CONCERNING...TORNADO WATCH 228...229...
   
   VALID 030340Z - 030545Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 228...229...CONTINUES.
   
   LONG-LIVED BOW ECHO THAT MOVED ACROSS SRN AR/NRN LA WAS CONTINUING
   TO DIMINISH LATE THIS EVENING AS IT MOVED ACROSS THE LWR MS VLY. 
   FEATURE PROBABLY HAS A SUFFICIENT COLD POOL THAT WHEN COMBINED WITH
   WEAKLY CAPPED MLCAPE OF 750-1500 J/KG PRESENT ACROSS CNTRL MS...A
   DMGG WIND/HAIL THREAT WILL BE MAINTAINED FOR A COUPLE MORE HOURS. 
   OTHERWISE...DOWNSTREAM AIR MASS... PARTICULARLY ACROSS AL HAS
   STABILIZED AS NOCTURNAL BOUNDARY LAYER COOLS.  WDLY SCTD TSTMS WILL
   REMAIN POSSIBLE AS LLVL WARM ADVECTION CONTINUES THROUGH THE NIGHT
   WITH A COUPLE OF STORMS PRODUCING HAIL OR PERHAPS GUSTY WINDS. 
   BUT...THE SVR THREAT...IN PARTICULAR THE TORNADO THREAT...WAS WANING
   ACROSS MS/AL.
   
   MEANWHILE...UPSTREAM...OUTFLOW BOUNDARY FROM MS VLY BOW HAS SPLAYED
   OUT ACROSS NRN LA WWD TO SOUTH OF KSHV THEN INTO A SFC LOW NE OF
   DALLAS.  CONSIDERABLE MOISTURE TRANSPORT/UPGLIDE CONTINUE ALONG THE
   NOSE OF 30-35 KT SWLY LLJ ATOP THIS BOUNDARY ACROSS FAR SRN AR AND
   NERN TX.  ANOTHER TSTM CLUSTER HAS FORMED INVOF THE SFC LOW/MCV OVER
   NCNTRL TX AND WILL TRANSLATE DOWNSTREAM...MERGING WITH TSTM CLUSTERS
   ACROSS SRN AR THROUGH AT LEAST 09Z.  
   
   TSTMS APPEAR THAT THEY WILL BE ROOTED JUST ABOVE THE SFC THE
   REMAINDER OF THE EVENING ACROSS NERN TX INTO SRN AR/NRN LA AS THE
   WARM SECTOR BECOMES INCREASINGLY CAPPED.  BUT...PCPN LOADING AND
   PRESENCE OF MODEST WLY FLOW ALOFT MAY YIELD DMGG WIND GUSTS. 
   OTHERWISE...SPORADIC LARGE HAIL CAN BE EXPECTED PARTICULARLY AS
   STORMS MERGE.  A BRIEF ISOLD TORNADO CANNOT BE RULED OUT...MAINLY IF
   STORMS CAN DEVELOP CLOSER TO THE E-W ORIENTED OUTFLOW BOUNDARY.
   
   ..RACY.. 05/03/2009
   
   
   ATTN...WFO...BMX...JAN...LZK...SHV...FWD...
   
   LAT...LON   33069690 33929378 33509027 33738661 32718708 32459078
               32159494 32159660 33069690