MESOSCALE DISCUSSION 0671
   NWS STORM PREDICTION CENTER NORMAN OK
   0631 PM CDT SAT APR 30 2011
   
   AREAS AFFECTED...CENTRAL AND NRN AR
   
   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 
   
   VALID 302331Z - 010000Z
   
   MUCH OF CENTRAL AND NRN AR IS BEING MONITORED FOR A SEVERE WEATHER
   WATCH ISSUANCE EARLY THIS EVENING.  SPC COORDINATION WITH AFFECTED
   WFOS MAY BE NEEDED SOON...WITH PROBABILITY OF A WATCH ISSUANCE BY
   00Z IS 80 PERCENT.
   
   REGIONAL RADAR IMAGERY AND LIGHTNING DATA SHOWED A CONTINUED
   INCREASE IN TSTM COVERAGE AND INTENSITY ACROSS WRN TO NERN AR DURING
   THE LAST 1-2 HOURS.  SLY WINDS INTO THIS REGION ARE RESULTING IN
   SURFACE DEWPOINTS RISING THROUGH THE 60S.  THIS COUPLED WITH
   MIDLEVEL LAPSE RATES OF 7-7.5 C/KM IS SUPPORTING MODERATE
   INSTABILITY /MLCAPE 1000-1500 J PER KG/ DEVELOPING NEWD.
   
   WHILE MUCH OF THIS REGION HAS BEEN CLOUDY THROUGH THE DAY AND
   INITIAL ACTIVITY LIKELY ROOTED ABOVE THE SURFACE...FORECAST
   SOUNDINGS SUGGEST THE WARM/MOIST BOUNDARY LAYER MAY BECOME REALIZED
   AS THE CAP BASED AROUND 700 MB IS REDUCED.  THIS PROCESS MAY BE
   UNDERWAY NOW...BASED ON THE INCREASE IN ACTIVITY AND IS LIKELY
   SUPPORTED BY A WEAK MIDLEVEL IMPULSE TRACKING NEWD ACROSS NERN TX. 
   EFFECTIVE BULK SHEAR TO AROUND 50 KT WILL SUPPORT ORGANIZED STORMS
   AND AS THE CAP WEAKENS...STORMS SHOULD BECOME SURFACE BASED.  THIS
   WILL RESULT IN AN INCREASED TORNADO POTENTIAL...IN ADDITION TO THE
   THREAT FOR HAIL AND DAMAGING WINDS.
   
   ..PETERS.. 04/30/2011
   
   
   ATTN...WFO...MEG...LZK...
   
   LAT...LON   34969029 34409185 34379419 35499347 36399262 36499007
               35739002 34969029