MESOSCALE DISCUSSION 1872
   NWS STORM PREDICTION CENTER NORMAN OK
   0730 PM CDT THU AUG 23 2007
   
   AREAS AFFECTED...CNTRL/SRN LWR MI...EXTREME NRN IND AND EXTREME NWRN
   OH
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 642...
   
   VALID 240030Z - 240200Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 642
   CONTINUES.
   
   LAST VESTIGES OF WHAT WAS A STRONG BOW ECHO THAT DEVELOPED OVER
   CHICAGOLAND WAS DIMINISHING OVER THE DETROIT METRO AREA.  BASED ON
   MESOANALYSIS AND UPSTREAM VWP...THE SURGE OF COOLER AIR THAT
   EMANATED FROM THIS TSTM COMPLEX APPARENTLY IS QUITE SHALLOW.  IN
   FACT...RENEWED STORMS THAT HAVE ORGANIZED RECENTLY IN SRN
   CHICAGOLAND PRODUCED WIND GUSTS OVER 60 MPH NORTH OF THE OUTFLOW
   BOUNDARY.  GIVEN PRONOUNCED ORGANIZATION TO THE LINEAR MCS OVER NERN
   IL AND MODEST INSTABILITY FEEDING THE STORMS...IT IS REASONABLE TO
   EXPECT DAMAGING WINDS AND ISOLD BOOKEND TORNADO THREATS TO EXPAND
   DOWNSTREAM ACROSS NWRN/NCNTRL INDIANA THROUGH MID-EVENING. 
   ATTM...IT APPEARS THE GREATEST PROBABILITY FOR DMGG WIND GUSTS WILL
   OCCUR FROM THE MERRILLVILLE/VALPARAISO REGIONS ESEWD TOWARD PLYMOUTH
   AND ROCHESTER INDIANA THROUGH 0130Z.  IT IS VERY LIKELY THAT THE
   STRONGEST PART OF THE BOW APEX WILL BE ALONG THE OUTFLOW BOUNDARY
   SITUATED ACROSS NRN INDIANA.
   
   ELSEWHERE...THE COLD POOL APPEARS DEEPER ACROSS LWR
   MI...PARTICULARLY N OF A LATITUDE OF KGRR AND KLAN.  OTHER THAN THE
   LINGERING THREAT FOR DMGG WINDS/HAIL VCNTY KDTW THROUGH
   0130Z...PRIMARY SVR THREATS SHOULD SKIRT THE IND/MI BORDER AND
   POINTS SWD.
   
   ..RACY.. 08/24/2007
   
   
   ATTN...WFO...CLE...DTX...IWX...GRR...
   
   42558679 43928369 43668260 42668246 41488321 41268528
   41228656