Cooler air has settled over southern Wisconsin for Today. This marks the beginning of a change in the upper level wind pattern or steering currents which drive the weather across the Upper Midwest and Wisconsin. The upper level winds will be more northwesterly during the next week, which will allow cooler air to make greater intrusions into the region.
The below graphic illustrates the transition zone between the unseasonably cool temperatures (blue and green), and the milder (purple and red) temperatures located to the west. Low pressure systems moving along this transition zone during the next week will result in a roller coaster ride of temperatures during the next week.
On Wednesday, increasing south winds will pull warmer temperatures temporarily back into southern Wisconsin. However, cooler temperatures will be poised in southern Canada to surge back into southern Wisconsin later in the week.
The below graphic illustrates the expected weather and high temperatures across southern Wisconsin this work week. Patchy frost is expected away from Lake Michigan Tonight.
NWS Milwaukee/Sullivan, WI