MESOSCALE DISCUSSION 2110
   NWS STORM PREDICTION CENTER NORMAN OK
   0539 AM CDT THU OCT 15 2009
   
   AREAS AFFECTED...PORTIONS SWRN AR...EXTREME NE TX...NRN LA...EXTREME
   W-CENTRAL MS.
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 151039Z - 151315Z
   
   CONDITIONS HAVE BECOME SOMEWHAT MORE FAVORABLE FOR ORGANIZED SVR
   THREAT IN CORRIDOR EXTENDING SEWD FROM PRESENT/LOOSELY-ORGANIZED
   CONVECTIVE COMPLEX OVER ARKLATEX REGION.  POTENTIAL EXISTS FOR THIS
   ACTIVITY TO GROW UPSCALE AND EVOLVE INTO MORE CONCENTRATED
   MCS...INCREASING DAMAGING WIND THREAT AS IT MOVES SEWD.
   
   MODIFIED RAOBS AND RUC SOUNDINGS INDICATE AVAILABLE/EFFECTIVE INFLOW
   LAYER WILL REMAIN CHARACTERIZED BY VERY MOIST/HIGH-THETAE CONDITIONS
   WITH RESULTANT BOOST IN AVAILABLE BUOYANCY IN SYSTEM RELATIVE SENSE.
    SFC DEW POINTS GENERALLY LOW-MID 70S F IN FOREGOING AIR MASS WILL
   OFFSET WEAK LAPSE RATES ALOFT ENOUGH TO SUPPORT 1000-200 J/KG MLCAPE
   THROUGH ABOUT 13-14Z...INCREASING THEREAFTER WITH DIURNAL HEATING. 
   MEANWHILE...MLCINH IS ALREADY WEAK AND SHOULD NOT CHANGE APPRECIABLY
   FOR ANOTHER 2-3 HOURS...GIVEN CONSTRAINTS IMPOSED BY MOISTURE ON
   DIABATIC COOLING.  OFFSETTING FACTORS WILL INCLUDE LITTLE OR NO
   APPRECIABLE EVAPORATE COOLING EFFECTS ON STORM-SCALE TO ACCELERATE
   DOWNDRAFTS GENERATED ALOFT...AND LACK OF STRONGER FLOW JUST ABOVE
   SFC FOR SUSTAINED/BROAD ZONE OF DOWNWARD MOMENTUM TRANSFER. 
   DAMAGING WIND THREAT THEREFORE IS TIED MORE TO SMALLER SCALE
   BOW/LEWP PROCESSES AND RELATED/LOCALIZED OUTFLOW SURGES.  MCS SHOULD
   CONTINUE TO MOVE GENERALLY PARALLEL TO AND INVOF
   DIFFUSE/QUASISTATIONARY SFC FRONTAL ZONE.  ALTHOUGH SFC WINDS WILL
   REMAIN WEAK...EFFECTIVE SHEAR 40-50 KT WILL AIR POTENTIAL STORM
   ORGANIZATION.  TAIL END OF MCS...ESPECIALLY WITH ANY
   PROPAGATIONAL/BACKBUILDING COMPONENT OF MOVEMENT...WILL REMAIN ON
   NERN EDGE OF FAVORABLE LOW LEVEL HODOGRAPH STRUCTURES. 
   THEREFORE...WHILE ADDITIONAL SUPERCELLS ARE POSSIBLE AND TORNADO
   RISK IS NON-ZERO...MAIN CONCERN WILL BE EPISODIC STG-SVR GUSTS.
   
   ..EDWARDS.. 10/15/2009
   
   
   ATTN...WFO...JAN...LZK...SHV...
   
   LAT...LON   33859445 33909272 33549172 32899085 32149070 31589192
               32119352 33209440 33859445