These images are for Saturday at 15Z on the 295K sfc. A gigantic area of rising motion was identified west of indiana. After identifying and tracking a vort max at 500 mb for 12 hours before and after 15Z, the second image is using those system relative winds to calculate omega. Basically it shows that the omega seen from straight pressure advection is mostly not really going on when you look at system relative flow. The system relative flow is just a little more parallel to the isobars. Kind of a let down? Maybe, but it explains why we are expecting a dry day (aside from lake effect) on Saturday.
Graphics created by Daniel Burgin