MESOSCALE DISCUSSION 1769
   NWS STORM PREDICTION CENTER NORMAN OK
   0943 PM CDT WED JUL 27 2011
   
   AREAS AFFECTED...NRN IL...E-CNTRL IA...FAR SRN WI
   
   CONCERNING...TORNADO WATCH 694...
   
   VALID 280243Z - 280345Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 694 CONTINUES.
   
   AN ORGANIZED CLUSTER OF TSTMS NEAR THE IL/WI BORDER HAS ACCELERATED
   EWD WITHIN THE PAST HR. EXTRAPOLATION OF CURRENT MOTION HAS IT
   REACHING WRN PORTIONS OF CHICAGOLAND AFTER 0330Z...WITH A PRIMARY
   THREAT OF DMGG WINDS. THE POTENTIAL FOR HAIL AND AN ISOLATED TORNADO
   WILL ALSO EXIST. 
   
   RECENT RADAR IMAGERY SUGGESTS COLD POOL IS RAPIDLY SPREADING
   S/EWD...WITH MOST NEW CONVECTIVE DEVELOPMENT FOCUSED ALONG THE ERN
   FLANK. KLOT 0.5 DEG BASE VELOCITY IMAGE SAMPLED A SWATH OF 50+ KT
   VELOCITY HEADING TOWARDS THE WRN/NRN SUBURBS OF THE CHICAGO METRO
   AREA. ALTHOUGH CINH HAS INCREASED IN RESPONSE TO THE LOSS OF
   DIABATIC HEATING...NEAR-SFC BASED PARCELS ARE STILL LIKELY GIVEN A
   VERY MOIST BOUNDARY LAYER AND STRONG S-SWLY INFLOW /20-30 KTS PER
   LOT VWP DATA/ IN THE 0-1 KM LAYER...SUPPORTING A CONTINUED THREAT OF
   DMGG WINDS. 
   
   FARTHER W...ACROSS E-CNTRL IA AND NWRN IL...CONVECTION CONTINUES TO
   BACKBUILD ALONG AN E-W SEGMENT FROM 15 W DBQ TO 30 W RFD. EMBEDDED
   ROTATION HAS OCCASIONALLY BEEN OBSERVED WITHIN THIS CLUSTER OF
   STORMS...WITH SOME POTENTIAL FOR AN ISOLATED TORNADO AND DMGG WIND
   GUSTS CONTINUING. HOWEVER...IT APPEARS THE PRIMARY THREAT HAS LIKELY
   TRANSITIONED TO HEAVY RAINFALL...SUPPORTED BY THE PRESENCE OF
   CLIMATOLOGICALLY HIGH PWAT VALUES.
   
   ..ROGERS.. 07/28/2011
   
   
   ATTN...WFO...LOT...MKX...DVN...ARX...
   
   LAT...LON   41689143 42679144 42538708 41538708 41689143