MESOSCALE DISCUSSION 1779
   NWS STORM PREDICTION CENTER NORMAN OK
   1151 PM CDT THU JUL 28 2011
   
   AREAS AFFECTED...NORTHERN IL/SOUTHERN LOWER MI/NORTHERN INDIANA
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 290451Z - 290615Z
   
   ASIDE FROM LOCALLY HEAVY RAINFALL...ISOLATED DAMAGING WINDS AND/OR A
   BRIEF TORNADO MAY BE POSSIBLE OVERNIGHT.
   
   POTENTIALLY AIDED BY A LOW AMPLITUDE IMPULSE PHASING WITH A MORE
   CONSEQUENTIAL EASTWARD-MOVING SHORTWAVE TROUGH OVER THE UPPER
   MIDWEST...SCATTERED TSTMS HAVE INCREASED TO A DEGREE OVER FAR
   NORTHERN IL /INCLUDING THE CHICAGO AREA/ RECENTLY WHILE OTHERWISE
   PERSISTING OVER THE PAST FEW HOURS ACROSS SOUTHERN LOWER MI. THESE
   STORMS ARE OCCURRING IN VICINITY OF A SURFACE BOUNDARY THAT EXTENDS
   WSW-ENE ACROSS THE REGION. IN PROXIMITY TO THIS BOUNDARY...THE
   AIRMASS REMAINS RELATIVELY WARM AND VERY MOIST WITH LOWER TO MIDDLE
   70S F SURFACE DEWPOINTS COMMON. WHILE SOME NEAR-SURFACE CINH
   EXISTS...REGIONAL WSR-88D VWPS ARE SAMPLING RELATIVELY STRONG SPEED
   SHEAR /ACCENTUATED BY A 30 KT LOW LEVEL JET AND 0-1 KM SRH OF
   100-200 M2 PER S2/ WITHIN AN OTHERWISE LARGELY UNIDIRECTIONAL WIND
   PROFILE. WITH A FEW WEAK/TRANSIENT SUPERCELL STRUCTURES HAVING
   ALREADY BEEN NOTED PER RADAR IMAGERY...A DAMAGING WIND AND/OR BRIEF
   TORNADO THREAT CANNOT BE RULED OUT OVERNIGHT. LOCALLY HEAVY RAINFALL
   WILL BE A CONCERN AS WELL.
   
   ..GUYER.. 07/29/2011
   
   
   ATTN...WFO...DTX...IWX...GRR...LOT...DVN...
   
   LAT...LON   41559006 42348956 42478780 42558621 42908399 42488323
               41908400 41408687 41308937 41559006