MESOSCALE DISCUSSION 1210
   NWS STORM PREDICTION CENTER NORMAN OK
   0315 PM CDT THU JUN 18 2009
   
   AREAS AFFECTED...SRN MN INTO NRN
   
   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 
   
   VALID 182015Z - 182145Z
   
   THE THREAT FOR SIGNIFICANT SUPERCELLS CAPABLE OF VERY LARGE
   HAIL...DAMAGING WINDS AND POTENTIALLY STRONG TORNADOES IS EXPECTED
   TO INCREASE ACROSS DISCUSSION AREA LATE THIS AFTERNOON INTO EVENING.
   A TORNADO WATCH HAS BEEN ISSUED ACROSS MN AND ANOTHER MAY WELL BE
   REQUIRED WITH TIME OVER PARTS OF IA.
   
   LATEST SURFACE ANALYSIS INDICATES A PERSISTENT MESOLOW NE OF TQE
   ALONG THE NOSE OF LOW-LEVEL THERMAL AXIS WHICH HAS DEVELOPED THROUGH
   ERN NEB INTO W-CNTRL IA.  MEANWHILE...HIGH-RESOLUTION RADAR AND
   SURFACE DATA INDICATE COMPOSITE OUTFLOW BOUNDARY RETREATING NWD AS A
   WARM FRONT THROUGH CNTRL IA.  AIR MASS TO THE E OF THIS BOUNDARY
   REMAINS QUITE MOIST WITH DEWPOINTS IN THE LOWER 70S.  MOREOVER...THE
   PRESENCE OF CONSIDERABLE DIABATIC HEATING SHOULD CONTINUE TO MODIFY
   THE CHARACTER OF THE BOUNDARY LAYER THROUGH THE REMAINDER OF THE
   AFTERNOON WITH ENVIRONMENT BECOMING MODERATELY TO STRONGLY UNSTABLE
   WITH MLCAPE OF 2000-4000 J/KG AND DECREASING CONVECTIVE INHIBITION.
   
   AFTERNOON WATER VAPOR IMAGERY INDICATES A COUPLE OF WEAK MIDLEVEL
   IMPULSES LOCATED UPSTREAM...ONE OVER SD AND THE OTHER OVER WRN/CNTRL
   NEB.  FORCING FOR ASCENT ASSOCIATED WITH THESE FEATURES COUPLED WITH
   SUSTAINED LOW-LEVEL CONVERGENCE ALONG COMPOSITE BOUNDARY SHOULD BE
   SUFFICIENT TO INITIATE SCATTERED STORMS BY LATE AFTERNOON OR EARLY
   EVENING.
   
   GIVEN THE DEGREE OF INSTABILITY...50-60 KT OF EFFECTIVE BULK SHEAR
   AND RATHER STRONG LOW-LEVEL SHEAR ON COOL SIDE OF
   BOUNDARY...ENVIRONMENT WILL SUPPORT INTENSE SUPERCELL DEVELOPMENT
   WITH THE THREAT FOR VERY LARGE HAIL...DAMAGING WINDS AND POSSIBLY
   STRONG TORNADOES.  THOUGH FORECAST STORM MOTIONS ARE LARGELY NORMAL
   TO ORIENTATION OF COMPOSITE BAROCLINIC ZONE...AIR MASS ON COOL SIDE
   OF BOUNDARY SHOULD BE SUFFICIENTLY MOIST/UNSTABLE TO SUSTAIN STORMS
   AND ATTENDANT TORNADO THREAT WELL TO THE E.
   
   ..MEAD.. 06/18/2009
   
   
   ATTN...WFO...DVN...ARX...MPX...DMX...FSD...
   
   LAT...LON   43049545 43649567 44299529 44869423 44629280 44079192
               42879180 42259215 41869315 42159455 43049545