MESOSCALE DISCUSSION 0429
   NWS STORM PREDICTION CENTER NORMAN OK
   0733 PM CDT THU APR 14 2011
   
   AREAS AFFECTED...CNTRL/WRN AR
   
   CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 
   
   VALID 150033Z - 150230Z
   
   SEVERE THUNDERSTORMS WITH A HISTORY OF PRODUCING TORNADOES OVER ERN
   OK...MOVING EWD AT 25 TO 35 KT...WILL CROSS THE OK/AR BORDER AFTER
   02Z AND MARCH ACROSS AR DURING THE MID/LATE EVENING AND OVERNIGHT
   HOURS. A TORNADO WATCH WILL LIKELY BE ISSUED.
   
   SFC DEWPOINTS IN THE LOWER 60S AHEAD OF THE DRYLINE WILL SHIFT EWD
   INTO AR AS A PACIFIC COLD FRONT OVER CNTRL OK OVERTAKES THE DRYLINE
   AND THE MOIST AXIS SHIFTS EWD. WITH STEEP MID-LEVEL LAPSE RATES IN
   PLACE...MLCAPE VALUES OF 1000 TO 2000 J/KG WILL OVERSPREAD AR INVOF
   THE MOIST AXIS. STRONG DEEP-LAYER WIND SHEAR /EFFECTIVE BULK SHEAR
   MAGNITUDES AROUND 60 KT/ WILL SUSTAIN THE ONGOING SEVERE CONVECTION
   INTO AR. WHILE THE ANTICIPATED CONVECTIVE MODE IS SOMEWHAT
   UNCERTAIN...HIGH-RESOLUTION WRF GUIDANCE CONTINUES TO SUGGEST
   UPSCALE GROWTH INTO A QLCS...ESPECIALLY ACROSS CNTRL AND NRN AR.
   THIS WILL LIKELY OCCUR AS DEEP-LAYER ASCENT STRENGTHENS IN RESPONSE
   TO THE APPROACH OF THE LEFT-EXIT REGION OF A 100-125-KT 250-MB JET
   STREAK. DAMAGING WINDS AND LARGE HAIL ARE EXPECTED TO ACCOMPANY
   THESE STORMS. EMBEDDED SUPERCELLS AND MESOVORTICES WILL BE
   ASSOCIATED WITH A TORNADO THREAT GIVEN INCREASING LOW-LEVEL
   CLOCKWISE CURVATURE IN HODOGRAPHS PER RUC FORECAST SOUNDINGS
   SUPPORTING EFFECTIVE STORM-RELATIVE HELICITY VALUES BETWEEN 300 AND
   500 M2 PER S2. THIS WILL OCCUR AS A S-SWLY LOW LEVEL JET BECOMES
   ESTABLISHED AFTER SUNSET. A TORNADO THREAT WILL ALSO BE ASSOCIATED
   WITH ANY DISCRETE SUPERCELLS LEADING OR SOUTH OF THE QLCS. WHILE THE
   THREAT FOR A STRONG TORNADO WILL EXIST ACROSS WRN AR PRIOR TO 05Z
   WITH MORE DISCRETE CONVECTION...THE CONVECTIVE EVOLUTION TOWARD A
   MORE LINEAR SYSTEM WILL LIKELY MITIGATE THIS POTENTIAL LATER IN THE
   NIGHT.
   
   ..COHEN.. 04/15/2011
   
   
   ATTN...WFO...LZK...SHV...TSA...
   
   LAT...LON   33859422 34629438 35639440 36219428 36429333 36069180
               33639186 33289334 33859422