MESOSCALE DISCUSSION 0274
   NWS STORM PREDICTION CENTER NORMAN OK
   0724 AM CDT MON MAR 18 2013
   
   AREAS AFFECTED...FAR SOUTHEAST OK/NORTHEAST TX AND AR/FAR NORTHERN
   LA TO WESTERN MS/TN
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 181224Z - 181500Z
   
   PROBABILITY OF WATCH ISSUANCE...40 PERCENT
   
   SUMMARY...SEVERE POTENTIAL...INITIALLY IN THE FORM OF HAIL...MAY
   DEVELOP/INCREASE THROUGH MID-LATE MORNING WITHIN A CORRIDOR FROM
   SOUTHEAST OK/FAR NORTHEAST TX INTO MUCH OF AR/PERHAPS FAR NORTHERN
   LA AND EVENTUALLY WESTERN PORTIONS OF MS/TN. A WATCH COULD BE NEEDED
   FOR PORTIONS OF THE REGION /MOST PROBABLE ACROSS AR INTO MS/ LATER
   THIS MORNING.
   
   DISCUSSION...EMBEDDED WITHIN BROAD/STRENGTHENING CYCLONIC FLOW
   ALOFT...A NNE-SSW ORIENTED BAND OF ELEVATED TSTMS ACROSS FAR
   EAST-CENTRAL/SOUTHEAST OK AS OF 1200Z APPEARS TO BE ASSOCIATED WITH
   AN EASTWARD-MOVING LOBE OF ASCENT PER WATER VAPOR IMAGERY. THESE
   STORMS ARE OCCURRING TO THE N/NW OF A FRONTAL BOUNDARY THAT ROUGHLY
   EXTENDS WSW-ENE ACROSS NORTHEAST TX/SOUTH-CENTRAL AR. THIS BOUNDARY
   DEMARCATES A HIGHER PW ENVIRONMENT WITH PREVALENT LOWER 60S F
   SURFACE DEWPOINTS TO ITS SOUTH. 
   
   IT SEEMS READILY PLAUSIBLE THAT STORMS MAY CONTINUE TO INCREASE IN
   COVERAGE/INTENSITY AS THE CURRENT TSTMS/ASSOCIATED ASCENT
   INCREASINGLY COINCIDE WITH A HIGHER MOISTURE CONTENT AIRMASS ACROSS
   THE ARKLATEX. WITH AMPLE SHEAR THROUGH THE CLOUD BEARING
   LAYER...VERY STEEP LAPSE RATES/MODERATE ELEVATED BUOYANCY ATOP A
   STABLE NEAR-SURFACE LAYER /NORTH OF THE SURFACE BOUNDARY/ MAY BE
   CONDUCIVE FOR TSTMS TO PRODUCE HAIL. THE 12Z OBSERVED SOUNDING FROM
   LITTLE ROCK INDICATED A 7.9 C/KM MID LEVEL LAPSE RATE WITH 1800+
   J/KG MUCAPE WITH EFFECTIVE SHEAR AROUND 35 KT...AN ENVIRONMENT
   POTENTIALLY CONDUCIVE FOR A FEW ELEVATED SUPERCELLS/SUSTAINED
   MULTICELLS. CURRENT THINKING IS THAT STORMS COULD SUBSEQUENTLY
   BECOME INCREASINGLY SURFACE BASED /WITH AT LEAST DAMAGING WINDS MORE
   OF A CONCERN/ BY AROUND LATE MORNING/EARLY AFTERNOON AS THEY SPREAD
   EAST-SOUTHEASTWARD TOWARD SOUTHEAST AR/WESTERN MS VICINITY.
   
   ..GUYER/EDWARDS.. 03/18/2013
   
   
   ATTN...WFO...MEG...JAN...LZK...SHV...TSA...
   
   LAT...LON   34139541 34899451 35369161 35328989 34249047 33499099
               33019203 33039454 34139541