MESOSCALE DISCUSSION 1967
   NWS STORM PREDICTION CENTER NORMAN OK
   0243 PM CDT SAT AUG 13 2011
   
   AREAS AFFECTED...PORTIONS OF SRN AR...W-CNTRL MS
   
   CONCERNING...HEAVY RAINFALL 
   
   VALID 131943Z - 132145Z
   
   THUNDERSTORMS COULD PRODUCE RAINFALL RATES REACHING 2 INCHES PER
   HOUR.
   
   A BAND OF ELEVATED CONVECTION ORIENTED NEARLY PARALLEL TO AN 850-MB
   FRONT EXTENDS FROM 25 WSW HOT TO 15 ENE GLH...WHILE THE ATTENDANT
   SFC FRONT LIES 30-45 MILES SOUTH OF THIS LINE. WEAK ISENTROPIC
   ASCENT ATOP THE SLOPING FRONT...OWING TO WLY TO WSWLY FLOW AROUND 10
   KT AOB 1.5 KM AGL PER SHREVEPORT VWP DATA...WILL LIKELY PROMOTE
   CONVECTIVE SUSTENANCE AMIDST 1500-3000 J/KG OF MUCAPE. WITH PW
   VALUES OF 2.00 TO 2.25 INCHES PER GPS DATA...AIDED BY LOW-LEVEL
   MOISTURE TRANSPORT WITHIN THE PREVIOUSLY MENTIONED LOW-LEVEL FLOW
   REGIME...HEAVY RAINFALL WILL BE A CONCERN WITH THE BAND OF
   CONVECTION. FURTHERMORE...THE NEARLY PARALLEL ORIENTATION OF THE
   MEAN CLOUD-BEARING FLOW TO THE 850-MB FRONT WILL PROMOTE CONVECTIVE
   TRAINING WHILE MESO-BETA ELEMENTS TRANSLATE ESEWD AROUND 20-25 KT
   DURING THE AFTERNOON.  ALSO...ABOVE-FREEZING TEMPERATURES ARE NOTED
   THROUGH A DEEP LAYER PER 12Z OBSERVED LITTLE ROCK SOUNDING AND RUC
   FORECAST SOUNDINGS -- I.E. FREEZING-LEVEL-HEIGHTS AOA 14 KM AGL --
   ENHANCING THE DEPTH OF COLLISION-COALESCENCE PROCESSES. THESE
   FACTORS COULD SUPPORT RAINFALL RATES REACHING 2 IN/HR ACROSS THE
   DISCUSSION AREA. ADDITIONAL ELEVATED CONVECTION WILL CONTINUE
   DEVELOPING SOUTH OF THE AFOREMENTIONED CONVECTIVE BAND ACROSS
   BRADLEY/CALHOUN COUNTIES...AND POTENTIALLY MOVE INTO ASHLEY/CHICOT
   COUNTIES...AND WILL ALSO POSE A THREAT FOR HEAVY RAINFALL. AN
   ISOLATED WET MICROBURST OR TWO COULD PRODUCE DMGG WIND
   GUSTS...THOUGH THE OVERALL THREAT SHOULD BE MITIGATED BY THE
   BOUNDARY-LAYER STABILIZING EFFECTS ASSOCIATED WITH
   CONVECTION-REINFORCING COLD POOL.
   
   ..COHEN.. 08/13/2011
   
   
   ATTN...WFO...JAN...LZK...SHV...
   
   LAT...LON   34469381 34449248 34019080 33439043 33109116 33389252
               34069368 34469381