MESOSCALE DISCUSSION 0399
   NWS STORM PREDICTION CENTER NORMAN OK
   0806 PM CDT TUE APR 20 2004
   
   AREAS AFFECTED...MO VALLEY REGION OF IA/NEB
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 96...
   
   VALID 210106Z - 210230Z
   
   WW SHOULD BE CONTINUED FOR ALL COUNTIES IN POTENTIAL PATH OF SEVERE
   TSTMS OVER NERN NEB.  SMALL COMPLEX OF SEVERE TSTMS HAS EVOLVED FROM
   INITIAL TORNADIC/ANTICYCLONIC SUPERCELL...AND SHOULD MOVE SEWD 30-35
   KT TOWARD PORTIONS BURT/ DOUGLAS/WASHINGTON COUNTIES
   NEB...HARRISON/SHELBY/POTTAWATOMIE COUNTIES IA.  THIS ACTIVITY IS
   MOVING ALONG SRN GRADIENT OF NW-SE ORIENTED SWATH OF SFC MOISTURE --
   PARALLEL TO MOIST AXIS OVER NWRN IA.  MODIFIED OAX RAOB INDICATES
   VERY STEEP MIDLEVEL LAPSE RATES OVER REGION AND CONTINUED POTENTIAL
   FOR LARGE HAIL.  DRY LOW LEVEL AIR JUST ABOVE SFC ALSO SUPPORTS
   DAMAGING WIND WITH THIS ACTIVITY AS IT MOVES ACROSS MO RIVER INTO
   IA.  WEAKENING TREND POSSIBLE IN ANOTHER 2 HOURS OR SO...ONCE INFLOW
   LAYER DIABATICALLY COOLS ENOUGH TO REMOVE SFC-BASED INSTABILITY.
   
   ..EDWARDS.. 04/21/2004
   
   
   ATTN...WFO...DMX...EAX...FSD...OAX...GID...
   
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