MESOSCALE DISCUSSION 0411
   NWS STORM PREDICTION CENTER NORMAN OK
   1247 PM CDT THU APR 09 2009
   
   AREAS AFFECTED...ERN OK
   
   CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 
   
   VALID 091747Z - 092015Z
   
   SEVERE STORMS ARE EXPECTED TO DEVELOP OVER E CNTRL OK BY 20-21Z.
   THREAT WILL EXIST FOR SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL AND
   A FEW TORNADOES. TORNADO WATCH WILL LIKELY BE NEEDED BY 19-20Z.
   
   THIS AFTERNOON A SHARPENING DRYLINE EXTENDS FROM DEEPENING SURFACE
   LOW IN SW KS SEWD THROUGH CNTRL OK THEN SWWD THROUGH N CNTRL AND W
   CNTRL TX. EAST OF THE DRYLINE...MULTILAYER CLOUD DECK WITH EMBEDDED 
   CONVECTION IS ADVANCING RAPIDLY EAST...ALLOWING FOR A CORRIDOR OF
   PARTIAL CLEARING AND DIABATIC HEATING FROM N CNTRL TX THROUGH E
   CNTRL OK. AXIS OF MID-UPPER 50S DEWPOINTS IS ADVECTING RAPIDLY NWD
   THROUGH ERN OK BENEATH VERY STEEP 8+ C/KM MID LEVEL LAPSE RATES. AS
   THE BOUNDARY LAYER CONTINUES TO WARM...MLCAPE FROM 1500-2000 J/KG
   WILL LIKELY DEVELOP LATER THIS AFTERNOON. OBJECTIVE  ANALYSIS
   INDICATES THE ATMOSPHERE IS STILL CAPPED DUE TO PRESENCE OF THE WARM
   EML. HOWEVER...AS AGEOSTROPHIC FORCING FOR ASCENT WITHIN EXIT REGION
   OF APPROACHING UPPER JET BEGINS TO OVERTAKE THE CONVERGENCE AXIS
   ALONG THE DRYLINE...THE CAPPING LAYER WILL LIKELY MOISTEN AND COOL
   SUFFICIENTLY FOR CONVECTIVE INITIATION BY 20-21Z. COUPLED LOW-MID
   LEVEL JET STRUCTURE WILL MAINTAIN LARGE LOW-LEVEL HODOGRAPHS AND
   FAVORABLE BULK SHEAR FOR SUPERCELLS CAPABLE OF PRODUCING VERY LARGE
   HAIL AND TORNADOES...INCLUDING POTENTIAL FOR ISOLATED STRONG
   TORNADOES.
   
   ..DIAL.. 04/09/2009
   
   
   ATTN...WFO...TSA...OUN...
   
   LAT...LON   36709592 36429521 35659481 34859503 34089582 34199705
               35289700 36279730 36679678 36709592