MESOSCALE DISCUSSION 1691
   NWS STORM PREDICTION CENTER NORMAN OK
   1015 PM CDT MON JUL 07 2003
   
   AREAS AFFECTED...NERN KS...SWRN AND CENTRAL NEB...WRN IA...EXTREME
   SERN SD
   
   CONCERNING...SEVERE TSTM POTENTIAL...HEAVY RAIN...SEVERE
   THUNDERSTORM WATCH 671...
   
   VALID 080315Z - 080545Z
   
   SEVERE MCS WITH HISTORY OF DAMAGING GUST REPORTS OF UP TO 78 KT --
   WILL MOVE EWD TO ENEWD ACROSS MUCH OF W-CENTRAL AND CENTRAL NEB
   THROUGH ABOUT 6Z.  THIS MCS SHOULD REMAIN SEVERE AT LEAST THAT
   LONG...WITH ADDITIONAL SIGNIFICANT WIND REPORTS POSSIBLE.  THEREFORE
   WW 675 NECESSARY FOR CENTRAL/ERN NEB EWD TOWARD MO VALLEY.
   
   ACTIVITY IS FORCED BY ASCENT ALONG STEEP LEADING-EDGE OUTFLOW
   SLOPE...AND REINFORCED BY STRONG/EXPANDING COLD POOL.  FAVORED
   PROPAGATION REGION WILL BE ZONALLY ORIENTED  LOW LEVEL BAROCLINIC
   ZONE ACROSS CENTRAL NEB.  IN THAT BAROCLINIC ZONE...RENEWED
   FRONTOGENESIS IS EVIDENT AND BACKED/ELY LOW LEVEL FLOW MAXIMIZES
   CONVERGENCE...LOW LEVEL SR INFLOW AND ENVIRONMENTAL SHEAR.  TSTMS
   WILL BE MOVING INTO QUITE FAVORABLY UNSTABLE AIR MASS WITH SFC DEW
   POINTS 60S TO LOW 70S F...8-9 DEG C/KM MIDLEVEL LAPSE RATES...AND
   MUCAPES 4000-5000 J/KG.  ALTHOUGH A BOW ECHO TORNADO OR A FEW LARGE
   HAIL EVENTS MAY OCCUR...GREATEST THREAT BY FAR IS WIND DAMAGE.
   
   MEANWHILE...SEVERE TSTMS MAY LINGER FOR ANOTHER COUPLE HOURS OVER
   PORTIONS OF NWRN KS...IN ENVIRONMENT OF WEAKER
   CONVERGENCE/FLOW/SHEAR AND LESS MOISTURE RELATIVE TO FARTHER N. 
   MODIFIED RAOBS AND MODEL SOUNDINGS...HOWEVER...SUGGEST SUFFICIENT
   INSTABILITY TO MAINTAIN SEVERE POTENTIAL WITH MUCAPE 2000-3000 J/KG.
    BOUNDARY LAYER DECOUPLING WILL ALLOW LLJ TO INCREASED TO AROUND 40
   KT -- ENHANCING SR INFLOW.
   
   HEAVY RAIN RATES OF 2-3 INCHES/HOUR ARE POSSIBLE WITH ANY OF THIS
   CONVECTION...GIVEN WEAK LOW-MIDLEVEL FLOW ABOVE LLJ...AMPLE INFLOW
   MOISTURE WITH NEB ACTIVITY...AND SLOW STORM MOTIONS WITH KS
   CONVECTION.
   
   ..EDWARDS.. 07/08/2003
   
   
   ATTN...WFO...DMX...FSD...OAX...GID...LBF...GLD...
   
   42420198 42860053 43009777 42879621 42389532 41649537
   40729578 40249796 40020036 42310040