MESOSCALE DISCUSSION 2228
   NWS STORM PREDICTION CENTER NORMAN OK
   1144 PM CDT SUN SEP 18 2005
   
   AREAS AFFECTED...ERN SD...SRN MN...IA...NRN MO
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 799...
   
   VALID 190444Z - 190615Z
   
   CONTINUE WW.
   
   MID TROPOSPHERIC WARM FRONT HAS BECOME FOCUS FOR INCREASING
   CONVECTIVE DEVELOPMENT NEAR/EAST OF THE MID MISSOURI VALLEY DURING
   THE PAST COUPLE OF HOURS.  THIS FEATURE NOW EXTENDS ROUGHLY FROM THE
   SIOUX FALLS AREA...NORTH OF DES MOINES...INTO WEST CENTRAL
   ILLINOIS...AND WILL GRADUALLY SHIFT NORTHEASTWARD THROUGH THE UPPER
   MISSISSIPPI VALLEY OVERNIGHT.
   
   WHILE CAPPING IS STRONGER TO THE SOUTH/WEST OF MID-LEVEL FRONTAL
   ZONE...FOCUSED CONVERGENCE ON NOSE OF LOW-LEVEL JET...NOW IN EXCESS
   OF 40 KT...IS OVERCOMING INHIBITION AND MAINTAINING CONVECTIVE
   CLUSTER NOW SPREADING ACROSS THE OMAHA AREA.  UNCERTAINTY EXISTS
   CONCERNING HOW LONG THIS CONVECTION WILL PERSIST.  HOWEVER...AS
   LOW-LEVEL JET CONTINUES TO SLOWLY VEER...NEW CONVECTION MAY CONTINUE
   TO INCREASE ACROSS CENTRAL IOWA BETWEEN NOW AND 06-08Z.  GIVEN
   MOISTURE AVAILABLE TO THIS ACTIVITY ...CONTRIBUTING TO MOST UNSTABLE
   CAPE OF 2000-3000 J/KG IN FAVORABLY SHEARED ENVIRONMENT...LARGE HAIL
   WILL REMAIN A THREAT IN STRONGEST STORMS.
   
   ..KERR.. 09/19/2005
   
   
   ATTN...WFO...DMX...FSD...OAX...
   
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