MESOSCALE DISCUSSION 1698
   NWS STORM PREDICTION CENTER NORMAN OK
   0252 AM CDT TUE JUL 08 2003
   
   AREAS AFFECTED...SERN SD...NRN/ERN IA
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 677...
   
   VALID 080752Z - 080945Z
   
   A BAND OF ELEVATED THUNDERSTORMS IS EXPECTED TO CONTINUE DEVELOPING
   ESEWD FROM SERN SD INTO NRN/CENTRAL IA OVER THE NEXT SEVERAL HOURS. 
   A NEW SEVERE THUNDERSTORM WATCH MAY BE NEEDED EAST OF WATCHES 675
   AND 677 WITHIN THE NEXT 1-2 HOURS.
   
   ELEVATED THUNDERSTORMS ARE OCCURRING IN THE WARM ADVECTION ZONE
   NORTH OF THE EAST/WEST ORIENTED WARM FRONT THAT EXTENDS ACROSS EAST
   NEB INTO SRN IA.  RUC FORECAST SOUNDINGS SHOW ELEVATED MUCAPE OF
   1500-2500 J/KG NORTH OF THE FRONT WITH LIFTED PARCELS ORIGINATING
   WITHIN THE 800-900 MB LAYER.  MID LEVEL LAPSE RATES AROUND 7.5 C/KM
   WILL ENHANCE UPDRAFT VELOCITY SUGGESTING CONTINUED SHORT-TERM THREAT
   FOR ISOLATED LARGE HAIL WITH STRONGEST CELLS. 
   
   RUC AND ETAKF MODEL FORECASTS INDICATE THIS BAND OF CONVECTION WILL
   GRADUALLY DEVELOP ESEWD ACROSS CENTRAL/ERN IA IN THE 09-12Z TIME
   FRAME. RECENT WIND SHIFT/TEMPERATURE FALL AT YKN AND APPARENT
   DEVELOPMENT OF A WAVE ON THE CONVECTIVE BAND OVER EXTREME SERN
   SD/NWRN IA SUGGESTS STORMS IN THIS REGION MAY BECOME ORIENTED MORE
   NORMAL TO THE WNWLY MID LEVEL FLOW AND BEGIN TO ACCELERATE
   ESEWD...WITH A COINCIDENT INCREASE IN DAMAGING WIND POTENTIAL. WE
   WILL CONTINUE TO MONITOR CONVECTIVE EVOLUTION ACROSS THIS REGION.
   
   IN ADDITION TO THE SEVERE THUNDERSTORM THREAT...HEAVY RAIN IS
   POSSIBLE ACROSS SERN SD INTO NWRN IA/NORTH CENTRAL IA WHERE TRAINING
   OF CELLS IS OCCURRING.
   
   ..WEISS.. 07/08/2003
   
   
   ATTN...WFO...DVN...ARX...MPX...DMX...FSD...OAX...ABR...LBF...
   
   43019932 43889929 44159758 43489451 42689111 41629044
   40969133 41739443 42669781