MESOSCALE DISCUSSION 2258
   NWS STORM PREDICTION CENTER NORMAN OK
   0523 PM CDT MON OCT 17 2011
   
   AREAS AFFECTED...ERN OK...N-CNTRL TX...FAR NWRN AR/SWRN MO
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 172223Z - 180030Z
   
   SCATTERED TO NUMEROUS TSTMS WILL LIKELY INITIATE ALONG AND BEHIND
   SHARP SEWD-MOVING COLD FRONT IN THE EARLY/MID-EVENING. PRIMARY
   THREATS WILL BE SEVERE HAIL AND PERHAPS LOCALLY DAMAGING WINDS. THE
   PROBABILITY OF A SEVERE TSTM WATCH ISSUANCE BY 00Z IS 40 PERCENT.
   
   22Z SURFACE ANALYSIS PLACED NE-SW ORIENTED COLD FRONT FROM THE
   OK/KS/MO BORDER AREA BISECTING OK TO A TRIPLE-POINT LOW JUST E OF
   SPS. ALTHOUGH AIR MASS IS QUITE WARM AHEAD OF THE FRONT...SURFACE
   DEW POINTS HAVE HELD IN THE 50S...WHICH HAS CONTRIBUTED TO A WEAKLY
   UNSTABLE AIR MASS WITH MLCAPE AOB 1000 J/KG. SHORT WAVE TROUGH NOW
   CENTERED OVER THE TX/OK PANHANDLES WILL TRACK SEWD INTO N-CNTRL TX
   THIS EVENING. ASCENT ASSOCIATED WITH THIS FEATURE AND CONVERGENCE
   ALONG THE FRONT WILL BE SUFFICIENT FOR TSTMS INITIATION BY 00Z AND
   LIKELY INCREASING RAPIDLY IN COVERAGE TOWARDS 03Z. HOWEVER...A WARM
   SECTOR CAPPING INVERSION NOTED IN ACARS DATA INVOF DFW AND
   ANAFRONTAL NATURE OF THE FORCING SUGGEST TSTM UPDRAFTS WILL REMAIN
   ALONG AND BEHIND THE COLD FRONT.
   
   STRONGEST MID-LEVEL FLOW WILL STAY CONFINED SW OF THE SHORT WAVE
   TROUGH. STILL...THE PRESENCE OF 40 KT W/SWLYS AT 6 KM AGL PER NORMAN
   AND TULSA VWP DATA SHOULD BE SUFFICIENT FOR UPDRAFT ROTATION WITH A
   THREAT FOR SEVERE HAIL. THE RAPID EVOLUTION TO A CLUSTER AND PERHAPS
   LINEAR CONVECTIVE MODE INFERS THE MAGNITUDE OF THE HAIL THREAT WOULD
   PEAK EARLY AND BECOME MARGINAL WITH TIME THIS EVENING.
   
   ..GRAMS.. 10/17/2011
   
   
   ATTN...WFO...SGF...SHV...TSA...FWD...OUN...
   
   LAT...LON   34329792 35679662 36999491 37149456 37119403 36839368
               36359382 34189517 32809613 32539696 32549769 32709840
               33209844 34329792