MESOSCALE DISCUSSION 2040
   NWS STORM PREDICTION CENTER NORMAN OK
   1245 AM CDT TUE AUG 23 2011
   
   AREAS AFFECTED...PORTIONS IA AND SRN MN.
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 230545Z - 230745Z
   
   EXPANDING TSTM CLUSTER OVER PORTIONS NWRN IA...SWRN MN AND EXTREME
   ERN SD MAY CONTINUE TO GROW UPSCALE WITH POTENTIAL FOR DAMAGING WIND
   AND OCNL LARGE HAIL EXTENDING SEWD FROM THERE.  COMPLEX SHOULD TURN
   SEWD ACROSS IA ALONG THERMAL/BUOYANCY GRADIENT NEAR WARM FRONT.
   
   ACTIVITY HAS DEVELOPED AWAY FROM APPRECIABLE SFC FOCI...E OF COLD
   FRONT AND W OF WARM FRONT...IN ZONE OF STG LOW-LEVEL WAA AND SUBTLE
   LOW-LEVEL CONFLUENCE.  AIR MASS IS CHARACTERIZED BY FAVORABLE LOW
   LEVEL MOISTURE...I.E. PW AROUND 1.5-1.75 INCHES BASED ON REGIONAL
   GPS READINGS AND FCST SOUNDINGS...AND ERN RIM OF 70S F SFC DEW
   POINTS.  MIDLEVEL DCVA/ASCENT PRECEDING STG SHORTWAVE TROUGH OVER
   DAKOTAS WILL SHIFT ESEWD ACROSS REGION...HELPING TO MAINTAIN STEEP
   LAPSE RATES.  IN CONJUNCTION WITH LARGE LOW-LEVEL THETAE...MLCAPE
   NEAR 2000 J/KG IS FCST IN PROSPECTIVE SEWD TRACK OF COMPLEX.  TSTM
   ACCESS TO SFC-BASED PARCELS MAY DEPEND ON DEPTH/STRENGTH FORCED
   ASCENT ALONG LEADING EDGE OF COLD POOL...GIVEN DIABATIC SFC COOLING
   AND RESULTING GRADUAL INCREASE OF MLCINH.  SUCH EXPANSIVE COLD POOL
   MAY BE DEVELOPING GIVEN SVR GUST OF 57 KT ALREADY MEASURED AT
   LYV...CLUSTERING NATURE OF TSTMS...AND GUST-FRONT SURGE ALREADY
   EVIDENT ON SW SIDE OF COMPLEX.  40-50 KT NWLY EFFECTIVE-SHEAR
   VECTORS ARE EXPECTED TO CONTINUE OVER THIS REGION IN SUPPORT OF TSTM
   ORGANIZATION.
   
   ..EDWARDS.. 08/23/2011
   
   
   ATTN...WFO...DVN...ARX...MPX...DMX...FSD...OAX...
   
   LAT...LON   40959499 41619523 42349562 43519639 43889584 44249556
               43869438 43419325 42639165 42219090 41209205 40779328
               40689448 40959499