MESOSCALE DISCUSSION 1077
   NWS STORM PREDICTION CENTER NORMAN OK
   0216 PM CDT FRI JUN 12 2009
   
   AREAS AFFECTED...PARTS OF CNTRL/SRN OK INTO NRN AND W-CNTRL TX
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 121916Z - 122045Z
   
   THE THREAT FOR SEVERE STORMS CAPABLE OF VERY LARGE HAIL...DAMAGING
   WINDS AND PERHAPS A FEW TORNADOES IS EXPECTED TO INCREASE THROUGH
   THE REMAINDER OF THE AFTERNOON.  CONVECTIVE TRENDS ARE BEING
   MONITORED FOR A POSSIBLE WW.
   
   A COMPLEX SURFACE PATTERN HAS EVOLVED TODAY IN WAKE OF AR BOW ECHO. 
   18Z MESOANALYSIS INDICATES THAT A THERMAL LOW HAS DEVELOPED OVER
   NWRN TX /SW OF SPS/ WITH AN ATTENDANT LOW-LEVEL CONFLUENT ZONE
   EXTENDING GENERALLY SWD W OF ABI AND SJT.  TRUE DRYLINE LAGGED
   CONFLUENCE ZONE BY A COUNTY OR SO.  THE NRN DELINEATION OF EFFECTIVE
   WARM SECTOR IS OUTFLOW BOUNDARY TRAILING AR BOW ECHO WHICH WAS
   OBSERVED TO BE MOVING SLOWLY SWD JUST TO THE S OF THE I-40 CORRIDOR
   OVER CNTRL OK.
   
   LATEST VISIBLE SATELLITE IMAGERY SHOWS A GROWING CUMULUS FIELD ALONG
   CONFLUENCE ZONE FROM E OF SJT TO NEAR GRAHAM TX WHERE UPSTREAM
   TEMPERATURES W OF DRYLINE HAVE REACHED 95-100 F.  BASED ON 12Z
   MAF/AMA AND 17Z OUN SOUNDINGS...THESE TEMPERATURES SHOULD BE
   SUFFICIENT TO INITIATE SURFACE-BASED STORMS.  WHILE MIDLEVEL HEIGHTS
   ARE SLOWLY RISING IN WAKE OF IMPULSE APPROACHING THE MID MS
   VALLEY...IT APPEARS THAT THE STRONG DIABATIC HEATING INVOF
   CONFLUENCE ZONE/DRYLINE AND/OR OUTFLOW BOUNDARY WILL BE SUFFICIENT
   TO INITIATE AT LEAST ISOLATED STORMS.
   
   MODIFYING 17Z OUN SOUNDING FOR CURRENT WARM SECTOR CONDITIONS YIELDS
   MLCAPE OF 3000-4000 J/KG.  THIS INSTABILITY COINCIDES WITH A
   QUASI-ZONAL BELT OF 40-50 KT MIDLEVEL FLOW /PER AREA
   PROFILERS/...RESULTING IN AN ENVIRONMENT QUITE SUPPORTIVE OF A FEW
   INTENSE SUPERCELLS.  VERY LARGE...DAMAGING HAIL WOULD BE THE PRIMARY
   SEVERE WEATHER THREAT...THOUGH TORNADOES WOULD BE POSSIBLE WITH ANY
   STORMS THAT CAN REMAIN MORE DISCRETE.
   
   ..MEAD.. 06/12/2009
   
   
   ATTN...WFO...TSA...FWD...OUN...EWX...SJT...
   
   LAT...LON   30069954 31549961 33699930 34919868 35179775 35249667
               35029573 34139581 33309663 32829790 31699853 30019906
               29869932 30069954