Meso-analysis is showing the negatives of a decaying MCS cluster moving through in the early afternoon. Here you can see what it does to CAPE values noting that most of Northern Illinois is nowhere near as stable as surrounding areas.
The are will need to clear out in order for destabilization to occur. This is known as “atmospheric recovery” so if you ever hear a forecast mention something about whether or not the atmosphere can recover in time, that is what they are talking about. Taking a look at the satellite shows the area socked in clouds which will greatly slow this process down. There does, however appear to be a couple small boundaries in northeast Iowa and Southwest Wisconsin. You can also see a larger boundary to the south as well. These smaller boundaries in IA/WI could be potential focal points for new storm development if the recovery occurs. Satellite loops suggest the area of clouds will indeed vacate the area by 3 or 4pm, but barely at the edge of peak heating it could be too little too late.
The best chance for storms in the Northern Illinois/Iowa/Wisconsin area appears to be late evening into the overnight hours, if at all. Still, trends will need to be monitored in case the atmosphere does recover quickly and boundary interaction sets off a new round of storms. Overall this is not looking like a great chase scenario. Follow the facebook page for more frequent updates. http://www.facebook.com/TornadoChasing
Visible satellite imagry can be found at: http://www.weather.cod.edu/satrad/ Just click 1km products, visible, and then the area you wish to see.