MESOSCALE DISCUSSION 0780
   NWS STORM PREDICTION CENTER NORMAN OK
   1233 PM CDT SAT MAY 09 2009
   
   AREAS AFFECTED...SRN AR...NRN LA...FAR NERN TX
   
   CONCERNING...SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY 
   
   VALID 091733Z - 091830Z
   
   SEVERE THREAT APPEARS TO BE INCREASING DOWNSTREAM OF ONGOING
   ELEVATED TSTM CLUSTER WITH ADDITIONAL CELLS DEVELOPING ALONG A
   QUASI-STATIONARY FRONT AND RESIDUAL OUTFLOW BOUNDARIES. AS MODERATE
   SURFACE-BASED INSTABILITY DEVELOPS ALONG THE SRN FRINGE OF STRONGER
   MID-LEVEL WLYS...THREATS FOR SEVERE HAIL AND DAMAGING WIND WILL
   INCREASE. A SEVERE TSTM WATCH WILL LIKELY BE ISSUED PRIOR TO 19Z.
   
   AS OF 1730Z...RADAR IMAGERY DEPICTED A SMALL MCS ACROSS SERN OK WITH
   ADDITIONAL CELLS RECENTLY DEVELOPING DOWNSTREAM ACROSS SERN AR/FAR
   NERN TX. 17Z SUBJECTIVE SURFACE ANALYSIS PLACES A WEAK MESOLOW INVOF
   TXK ALONG A RESIDUAL W-E ORIENTED OUTFLOW BOUNDARY STRETCHING
   TOWARDS GLH...WITH A QUASI-STATIONARY FRONT LOCATED FROM AROUND 20 S
   MEM TO HOT TO NEAR PRX. MODIFIED 12Z RAOBS AND RUC FORECAST
   SOUNDINGS SUGGEST LIFTED MOST UNSTABLE PARCELS ARE ELEVATED N OF THE
   FRONTAL BOUNDARY. AS SUCH ACTIVITY N OF THIS BOUNDARY MAY YIELD
   MARGINALLY SEVERE HAIL. FARTHER S...SURFACE-BASED DESTABILIZATION
   SHOULD RESULT IN MLCAPES INCREASING TO 1000 TO 2000 J/KG. ALTHOUGH
   LOW-LEVEL FLOW IS WEAK /PER AREA PROFILERS AND VWPS/...30-40 KT WLYS
   AT 500 MB WILL BE SUFFICIENT FOR ORGANIZED CLUSTERS/LINE SEGMENTS
   WITH EMBEDDED SUPERCELL STRUCTURES. AS SUCH...SEVERE HAIL AND
   DAMAGING WIND WILL BE THE PRIMARY THREATS.
   
   ..GRAMS.. 05/09/2009
   
   
   ATTN...WFO...MEG...JAN...LZK...SHV...
   
   LAT...LON   34289089 33639068 32829098 32409148 32379230 32289348
               32489464 32879516 33249514 33749410 34239290 34349127
               34289089