MESOSCALE DISCUSSION 2129
   NWS STORM PREDICTION CENTER NORMAN OK
   0158 PM CDT MON OCT 22 2007
   
   AREAS AFFECTED...SRN/ERN LA INTO MS
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 221858Z - 222030Z
   
   A GRADUAL INCREASE IN THUNDERSTORM DEVELOPMENT IS EXPECTED THROUGH
   THE PEAK AFTERNOON HEATING.  TRENDS ARE BEING MONITORED FOR AN
   INCREASING SEVERE THREAT AND THE POSSIBILITY OF A WW.
   
   IN A RELATIVELY NARROW PRE-FRONTAL CORRIDOR ACROSS THE LOWER
   MISSISSIPPI VALLEY...BREAKS IN CLOUD COVER HAVE ALLOWED SUFFICIENT
   SURFACE HEATING TO REDUCE INHIBITION TO NEGLIGIBLE LEVELS.  AND
   THIS...IN CONJUNCTION WITH LARGE-SCALE FORCING FOR UPWARD VERTICAL
   MOTION ASSOCIATED WITH WEAK WARM ADVECTION...APPEARS TO BE
   SUPPORTING INCREASING THUNDERSTORM ACTIVITY ACROSS SOUTH CENTRAL
   LOUISIANA INTO SOUTHWESTERN MISSISSIPPI.  WHILE THIS IS STILL
   GENERALLY TO THE NORTH OF EXTENSIVE CONVECTIVE DEVELOPMENT OVER THE
   NORTH CENTRAL GULF OF MEXICO INTO CENTRAL GULF COASTAL AREAS...WHICH
   IS CUTTING OFF INFLUX OF MID/UPPER 70S F DEW POINTS INTO INLAND
   AREAS...DEW POINTS ACROSS THE LOWER MISSISSIPPI VALLEY ARE GENERALLY
   IN THE LOWER 70S.  
   
   GIVEN AT LEAST MODEST CLOCKWISE-CURVED HODOGRAPHS BENEATH 20-30 KT
   SOUTHERLY 850 FLOW...THE BOUNDARY LAYER WITH HIGH MOISTURE CONTENT
   AND HIGH RELATIVE HUMIDITIES APPEARS FAVORABLE FOR THE DEVELOPMENT
   OF ISOLATED TORNADOES.  MIXED LAYER CAPE IS ONLY ON THE ORDER OF 500
   J/KG DUE TO WEAK MID-LEVEL LAPSE RATES AHEAD SLOWLY DIGGING UPSTREAM
   TROUGH.  BUT...DEEP LAYER SHEAR BENEATH 50 KT CYCLONIC 500 MB FLOW
   IS STRONG AND FAVORABLE FOR SUPERCELLS...AS ACTIVITY SPREADS NORTH
   NORTHEASTWARD THIS AFTERNOON.
   
   ..KERR.. 10/22/2007
   
   
   ATTN...WFO...MEG...JAN...LIX...LCH...SHV...
   
   30579264 31869182 32789135 33829092 34298981 34238881
   32758890 31378989 30389047 29459196