MESOSCALE DISCUSSION 1663
   NWS STORM PREDICTION CENTER NORMAN OK
   0638 PM CDT FRI JUL 24 2009
   
   AREAS AFFECTED...CENTRAL/SOUTHERN IA AND FAR NORTHERN MO
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 242338Z - 250115Z
   
   MONITORING FOR SIGNS OF INCREASING DEEP CONVECTIVE DEVELOPMENT
   ACROSS IA EARLY THIS EVENING. ADDITIONAL/IMMINENT DEVELOPMENT WOULD
   LIKELY PROMPT A WATCH ISSUANCE.
   
   REMOVED FROM THE MORE APPRECIABLE LARGE SCALE FORCING FOR ASCENT
   OVER THE UPPER MISSISSIPPI RIVER VALLEY...STORMS HAVE STRUGGLED TO
   DEVELOP THUS FAR WEST-SOUTHWESTWARD ALONG SURFACE FRONTAL
   ZONE/PREFRONTAL TROUGH ANGLING NORTHEAST-SOUTHWESTWARD ACROSS IA.
   ACCORDINGLY...ASSOCIATED CU FIELD HAS REMAINED RELATIVELY FLAT SINCE
   MID AFTERNOON PER VISIBLE SATELLITE IMAGERY...ALTHOUGH A RECENT
   TREND OF MODEST VERTICAL DEVELOPMENT HAS BEEN NOTED ACROSS PORTIONS
   OF NORTH CENTRAL TO NORTHEAST IA...MAINLY IMMEDIATELY WEST OF
   EXISTING TORNADO WATCH 619. WITH AROUND 70F SURFACE DEWPOINTS AND A
   WEAKLY CAPPED/MODERATE TO STRONG UNSTABLE BOUNDARY LAYER IN
   PLACE...FRONTAL CONVERGENCE/AT LEAST GLANCING LARGE SCALE FORCING
   FOR ASCENT MAY PROVE SUFFICIENT FOR AN INCREASING SEVERE THREAT THIS
   EVENING ACROSS IA...WITH SEVERE HAIL/DAMAGING WINDS AS THE PRIMARY
   RISKS. LATEST SREF MULTI-MEMBER GUIDANCE...AND VARIOUS 12Z HIGH-RES
   4KM MODELS SUCH AS WRF-NMM/NSSL/ARW...ARE STRONGLY SUPPORTIVE OF
   INCREASING/SCATTERED TSTM DEVELOPMENT ACROSS PORTIONS OF
   CENTRAL/SOUTHERN IA THROUGH THE 00Z-03Z TIMEFRAME.
   
   ..GUYER.. 07/24/2009
   
   
   ATTN...WFO...DMX...EAX...OAX...
   
   LAT...LON   41939577 42539470 42699251 40679285 40439518 41939577