MESOSCALE DISCUSSION 0832
   NWS STORM PREDICTION CENTER NORMAN OK
   0117 PM CDT FRI MAY 15 2009
   
   AREAS AFFECTED...PARTS OF THE UPPER MS RIVER VALLEY
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 151817Z - 151915Z
   
   TSTM INITIATION SHOULD COMMENCE BY 20Z WITH AN INCREASING POTENTIAL
   FOR MAINLY LARGE HAIL EVOLVING AS STORMS MATURE IN THE LATE
   AFTERNOON HOURS ACROSS A SIZEABLE PART OF MN.
   
   LATEST SATELLITE IMAGERY SHOWS A SWELLING CU FIELD FROM NRN MN SSWWD
   INTO NERN NE.  RECENT SURFACE ANALYSIS SHOW A NARROW TONGUE OF
   LOW-MID 50S F DEWPOINTS ALONG AND AHEAD OF A PRESSURE
   TROUGH/WIND-SHIFT OVER PARTS OF W-CNTRL AND SWRN MN.  FURTHER W
   ACROSS EXTREME SERN ND INTO ERN SD...A COLD FRONT IS BEGINNING TO
   SURGE ESEWD NOTED BY ENHANCED NWLY WIND GUSTS BEHIND THE FRONT. 
   WITH APPROACH OF SHORTWAVE TROUGH FROM THE W...INCREASING LARGE
   SCALE ASCENT ALONG WITH CONTINUED LOW LEVEL CONVERGENCE INVOF
   PREFRONTAL SURFACE TROUGH/WIND-SHIFT WILL COMBINE WITH DIABATIC
   HEATING TO FAVOR TSTM DEVELOPMENT IN THE NEXT FEW HOURS.
   
   WARMING SURFACE TEMPS WELL INTO THE 60S AND 70S F...COMBINED WITH
   COOL MID-LEVEL TEMPS OBSERVED ON MPX 12Z RAOB /-18 C AT 500MB/ WILL
   CONTRIBUTE TO A N-S CORRIDOR OF WEAK TO MODERATE CONVECTIVE
   INSTABILITY /UP TO 1000 J/KG SBCAPE/ DEVELOPING AHEAD OF PREFRONTAL
   TROUGH.  STRONG CLOUD BEARING SHEAR /40-50 KTS/ WILL PROMOTE STORM
   ORGANIZATION WITH TIME.  AS SUCH...A BROKEN BAND OF SEMI-DISCRETE
   STORMS ARE EXPECTED TO DEVELOP WITH THE STRONGER STORMS CAPABLE OF
   MAINLY A LARGE HAIL THREAT...ESPECIALLY WITH ANY STORMS EXHIBITING
   SUPERCELL STRUCTURE.
   
   ..SMITH.. 05/15/2009
   
   
   ATTN...WFO...DLH...MPX...FGF...FSD...
   
   LAT...LON   46329303 44319437 43209587 43139634 43429664 47949504
               48369425 48029321 47589288 46329303