MESOSCALE DISCUSSION 1648
   NWS STORM PREDICTION CENTER NORMAN OK
   0948 AM CDT SUN JUL 06 2003
   
   AREAS AFFECTED...ERN IA...NE MO...NRN IL...SE WI
   
   CONCERNING...SEVERE THUNDERSTORM POTENTIAL 
   
   VALID 061448Z - 061645Z
   
   WW MAY BE NEEDED WITHIN THE NEXT 1 TO 2 HOURS.
   
   MID-LEVEL SHORT WAVE TROUGH/JET STREAK AND ASSOCIATED CENTER OF
   CYCLONIC VORTICITY ARE READILY EVIDENT IN LATEST SATELLITE AND RADAR
   IMAGERY OVER EASTERN IOWA.  SYSTEM IS STEADILY PROGRESSING EASTWARD
   ...AND WILL CONTINUE ACROSS THE MISSISSIPPI RIVER INTO SOUTHERN
   WISCONSIN AND NORTHERN ILLINOIS BY THE 18-20Z TIME FRAME.  FORCING
   FOR UPWARD VERTICAL MOTION IN ZONE OF DIFFERENTIAL POSITIVE
   VORTICITY ADVECTION APPEARS LIKELY TO BECOME PRIMARY FOCUS FOR
   INCREASING/INTENSIFYING CONVECTIVE DEVELOPMENT NEXT FEW HOURS. THIS
   IS EXPECTED TO MAINLY OCCUR ALONG/EAST OF THE MISSISSIPPI RIVER FROM
   PARTS OF WEST CENTRAL ILLINOIS INTO SOUTHERN WISCONSIN...WHERE
   BOUNDARY LAYER STABILIZED BY NOCTURNAL COOLING AND PREVIOUS
   CONVECTIVE OUTFLOW IS RECEIVING STRONG DAYTIME HEATING.
   
   AS SURFACE TEMPERATURES CLIMB INTO THE LOWER/MID 80S...MEAN MIXED
   LAYER CAPE APPEARS LIKELY TO INCREASE IN EXCESS OF 2000 J/KG...
   SUPPORTIVE OF VIGOROUS UPDRAFTS WITH HEAVY RAINFALL.  VERTICAL SHEAR
   ASSOCIATED WITH 35-40 KT MID-LEVEL JET MAY ENHANCE POTENTIAL FOR
   HAIL...THOUGH THIS MAY BE MARGINALIZED BY WARM THERMODYNAMIC
   PROFILES.  LOW-LEVEL FLOW IS WEAK...BUT AS CONVECTIVE CLUSTER SLOWLY
   EVOLVES...RELATIVE HUMIDITIES IN LOWER/MID-LEVELS APPEAR LOW ENOUGH
   TO SUPPORT SUBSTANTIAL SURFACE COLD POOL WHICH MAY BE ACCOMPANIED BY
   DAMAGING WINDS ALONG ASSOCIATED GUST FRONT.  THIS SHOULD SPREAD INTO
   AREAS NEAR/SOUTHWEST OF CHICAGO BY AROUND 20Z.
   
   ..KERR.. 07/06/2003
   
   
   ATTN...WFO...LOT...ILX...MKX...LSX...DVN...ARX...
   
   41389121 42159076 42859070 43279003 43278877 42568829
   41818796 40468869 39808963 39599116 40009234 40659173