MESOSCALE DISCUSSION 1459
   NWS STORM PREDICTION CENTER NORMAN OK
   1015 PM CDT THU JUN 30 2011
   
   AREAS AFFECTED...NERN-ERN IL / NWRN-WRN IND
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 010315Z - 010415Z
   
   STORMS CAPABLE OF ISOLD LARGE HAIL AND STRAIGHT-LINE WIND DAMAGE MAY
   CONTINUE SWD INTO DOWNSTATE IL PARALLELING THE IND/IL BORDER REGION.
   A NEW WW MAY NEED TO BE CONSIDERED S OF THE EXISTING SEVERE
   THUNDERSTORM WATCH 579 LOCATED OVER NERN IL/NWRN IND IN ORDER TO
   ADDRESS THIS POTENTIAL THREAT IF STORMS MAINTAIN THEIR INTENSITY.
   
   SURFACE ANALYSIS PLACES A WARM FRONT/BAROCLINIC ZONE EXTENDING NORTH
   TO SOUTH ALONG THE IND/IL BORDER.  THE AIRMASS TO THE W ON THE ERN
   PERIPHERY OF A STOUT PLAINS EML IS VERY UNSTABLE ACCORDING TO THE
   00Z DVN-ILX RAOBS.  STRONGLY VEERING DIRECTIONAL COMPONENT TO
   TROPOSPHERIC FLOW INCREASING WITH HEIGHT THROUGH THE MID-LEVELS WILL
   FAVOR ORGANIZED STORMS.  KLOT RADAR IMAGERY HAVE SHOWN PULSATING
   NATURE OF THE SUPERCELLS OVER THE SRN LAKE MICH/GREATER CHICAGO
   METRO VICINITY THE PAST FEW HOURS.  REPORT OF BASEBALL SIZE HAIL IN
   THE CHICAGO METRO AND A MEASURED WIND GUST TO 94 MPH AT WAUKEGAN
   HARBOR HAVE OCCURRED WITH THESE STORMS AT THEIR MOST INTENSE PHASE. 
   THIS PULSATING TREND /ALBEIT SUBDUED COMPARED TO EARLIER/ MAY
   CONTINUE OVER THE NEXT HOUR OR TWO AS THE STORMS MAINTAIN A FEED OF
   RICH/UNSTABLE PARCELS NEAR-OVERTOP CONSOLIDATING LAKE
   BREEZE/CONVECTIVE OUTFLOW AS IT MOVES SWD IMMEDIATELY AHEAD OF THE
   STORMS.  A GRADUAL WEAKENING TREND IS EXPECTED AS STORMS OUTRUN AND
   MOVE AWAY FROM A VERY UNSTABLE RESERVOIR OF HIGH THETA-E AIR
   CENTERED NEAR THE IA/IL/WI BORDER.
   
   ..SMITH.. 07/01/2011
   
   
   ATTN...WFO...IWX...IND...LOT...ILX...
   
   LAT...LON   39078867 40668846 41888785 41928720 41088706 39258718
               38838772 39078867