MESOSCALE DISCUSSION 0828
   NWS STORM PREDICTION CENTER NORMAN OK
   0152 PM CDT FRI MAY 20 2011
   
   AREAS AFFECTED...CNTRL KS...S-CNTRL NEB...NWRN OK
   
   CONCERNING...SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY 
   
   VALID 201852Z - 202045Z
   
   CONTINUED DESTABILIZATION ALONG COLD FRONT WILL HELP FOSTER TSTM
   DEVELOPMENT THIS AFTERNOON WITH PRIMARY INITIAL RISK OF SEVERE HAIL.
   THE PROBABILITY OF A SEVERE TSTM WATCH BEING ISSUED BY 21Z IS 60
   PERCENT.
   
   18Z SUBJECTIVE SURFACE ANALYSIS PLACED A PAIR OF 1003 MB CYCLONES
   NEAR RSL AND 30 NNW GAG ALONG A N/S-ORIENTED COLD FRONT FROM THE
   CNTRL INTO THE SRN PLAINS. SURFACE HEATING HAS BECOME MORE ROBUST
   DURING THE PAST COUPLE OF HOURS AS AN EXPANSIVE CIRRUS CANOPY
   ASSOCIATED WITH A LARGE-SCALE MCS OVER THE ERN GREAT PLAINS HAS
   GRADUALLY SHIFTED EWD. A NARROW AXIS OF A MARGINALLY UNSTABLE AIR
   MASS WITH MLCAPE AROUND 500 J/KG HAS DEVELOPED IMMEDIATELY AHEAD OF
   THE COLD FRONT WHERE SURFACE TEMPERATURES HAVE WARMED INTO THE
   MIDDLE 70S.
   
   SHOWERS/TSTMS HAVE RECENTLY COMMENCED ALONG THE FRONT FROM CNTRL KS
   INTO W-CNTRL OK...AN HOUR OR TWO EARLIER THAN LATEST
   CONVECTION-ALLOWING HRRR AND WRF-NMM/NSSL GUIDANCE. CONTINUED
   DESTABILIZATION WILL SUPPORT INCREASINGLY BUOYANT UPDRAFTS THROUGH
   THE AFTERNOON AMIDST STRONG DEEP-LAYER SPEED SHEAR.
   HOWEVER...VEER-BACK-VEER WIND PROFILES INDICATED IN AREA
   PROFILERS...ALONG WITH WEAK LOW-LEVEL FLOW AND DEEP-LAYER SHEAR
   VECTORS ORIENTED NEARLY PARALLEL TO THE INITIATING BOUNDARY SHOULD
   RESULT IN A MORE CLUSTER TYPE CONVECTIVE MODE AND SERVE TO TEMPER A
   MORE WIDESPREAD LARGE HAIL THREAT.
   
   ..GRAMS.. 05/20/2011
   
   
   ATTN...WFO...TOP...ICT...OUN...GID...DDC...
   
   LAT...LON   37209980 38849927 40699918 41049909 41219865 41059823
               40469798 38799791 36319878 36059918 36109971 36609990
               37209980