MESOSCALE DISCUSSION 0673
   NWS STORM PREDICTION CENTER NORMAN OK
   0847 PM CDT SAT APR 30 2011
   
   AREAS AFFECTED...CENTRAL AR
   
   CONCERNING...TORNADO WATCH 258...
   
   VALID 010147Z - 010245Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 258 CONTINUES.
   
   RECENT TRENDS PER LIT WSR-88D INDICATED THE STORM OVER GARLAND
   COUNTY AR WAS BECOMING SUPERCELLULAR /INFLOW NOTCH AND LOW LEVEL
   ROTATION/ AND TRACKING ESE AT 25 KT.  00Z LIT SOUNDING SHOWED THE
   CAP HAD WEAKENED SINCE 12Z WITH A RATHER MOIST BOUNDARY LAYER AS
   CURRENT SURFACE OBSERVATIONS ACROSS CENTRAL/SRN AR INDICATED AN
   INCREASE IN SURFACE DEWPOINTS TO THE UPPER 60S.  THIS IS
   CONTRIBUTING TO A MODERATELY UNSTABLE AIR MASS.  MEANWHILE...
   STRENGTHENING SWLY LLJ TO 40 KT PER LIT WSR-88D VWP DATA IS
   RESULTING IN INCREASING LOW LEVEL SHEAR /SFC-1 KM SRH 420 M2 PER
   S2/.  THIS COMBINED WITH AFOREMENTIONED THERMODYNAMICS AND OBJECTIVE
   ANALYSES SHOWING EFFECTIVE INFLOW IS SURFACE BASED PROVIDES CONCERN
   THAT THIS STORM COULD PRODUCE A TORNADO.
   
   OTHER STORMS DEVELOPING AND/OR MOVING INTO CENTRAL AR WILL NEED TO
   BE MONITORED FOR SIMILAR TRENDS AND THREAT.
   
   ..PETERS.. 05/01/2011
   
   
   ATTN...WFO...LZK...SHV...
   
   LAT...LON   35259278 35459201 35309130 34219132 34109201 33889315
               34219440 34649438 35109327 35259278