Originally it was looking very warm tomorrow in almost all of northern IL, but man, trends aren't looking good for that now. The surface low is pretty far west during the day and on a weakening trend with time, so the warm front doesn't get a decisive push northward through the area. This setup screams of a large temperature gradient setting up, reinforced by a cold Lake Michigan. A little tricky to get too specific but there is a plausible scenario where O'Hare doesn't get out of the 40s and it's like 65 here or just south of here. In any case, expect a large temperature gradient in the LOT cwa tomorrow.