A number of the more notorious tornado outbreaks in the region have had this... like a dryline or at least hybrid dryline feature. Palm Sunday had it. Another one that had, and one of the more extreme examples of it, was 4/3/1956. I remember seeing a midday surface map with dews in the 60s in places like Milwaukee and Chicago and dews in the 20s around Rockford and Madison, and they were still out ahead of the synoptic cold front.