MESOSCALE DISCUSSION 0762
   NWS STORM PREDICTION CENTER NORMAN OK
   0105 PM CDT FRI MAY 08 2009
   
   AREAS AFFECTED...IA
   
   CONCERNING...SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY 
   
   VALID 081805Z - 081930Z
   
   SEVERE THREAT WILL INCREASE ACROSS IA AHEAD OF A VIGOROUS SHORT WAVE
   TROUGH APPROACHING FROM THE NRN PLAINS. ALTHOUGH INSTABILITY SHOULD
   REMAIN MODEST...INTENSE MID-LEVEL FLOW WILL SUPPORT TSTM
   ORGANIZATION AND PROBABLE HAIL DEVELOPMENT INITIALLY. A SEVERE TSTM
   WATCH WILL LIKELY BE NEEDED BY 20Z.
   
   LATEST SUBJECTIVE SURFACE ANALYSIS PLACED A 1004 MB CYCLONE NEAR TQE
   DOWNSTREAM OF A POTENT SHORT WAVE TROUGH OVER THE NRN PLAINS /PER
   WATER VAPOR IMAGERY/. A QUASI-STATIONARY FRONT WAS DRAPED EWD FROM
   THE LOW ALONG THE US-20 CORRIDOR...WITH A COLD FRONT SWWD INTO NRN
   KS. STRONGLY FORCED ASCENT SHOULD RESULT IN TSTM COVERAGE INCREASING
   INVOF THESE BOUNDARIES OVER IA. INSTABILITY AND LOW-LEVEL FLOW BOTH
   APPEAR WEAK IN THE WAKE OF LARGE-SCALE MCS CENTERED OVER THE MID-MO
   RIVER VALLEY. HOWEVER...CONTINUED DAYTIME HEATING MAY RESULT IN
   MLCAPES APPROACHING 1000 J/KG BY LATE AFTERNOON. ALTHOUGH LOW-LEVEL
   WINDS SHOULD REMAIN MODEST...MODEL FORECASTS ARE QUITE CONSISTENT ON
   STRENGTHENING 500 MB WINDS TO AOA 80 KT OVER MUCH OF NEB THIS
   AFTERNOON AND ACROSS THE MO RIVER VALLEY BY 00Z. THIS INCREASE IN
   SPEED SHEAR ALONG WITH NEARLY STRAIGHT-LINE HODOGRAPHS SHOULD
   INITIALLY FAVOR SPLITTING CELLS PRODUCING SEVERE HAIL. WITH
   TIME...UPSCALE GROWTH AMIDST THE STRONG ASCENT MAY LEAD TO A FORCED
   LINE WITH STRONG/SEVERE WIND GUSTS.
   
   ..GRAMS.. 05/08/2009
   
   
   ATTN...WFO...DVN...ARX...DMX...FSD...OAX...
   
   LAT...LON   43279218 42919097 41469127 41049185 40739268 40789397
               41089536 41429588 42179605 42879517 43199337 43279218