Low pressure traveling south of Wisconsin will likely bring wintery weather back to southern Wisconsin late Monday night into Wednesday. A large, sprawling area of high pressure will build into southern Canada Monday and Monday Night. This will act as a source of cold air from the north. At the same time, low pressure will develop in the central Plains, helping to strengthen a warm front which will extend eastward across the central Mississippi Valley.
This warm front and the low pressure moving along it will act as the focus for widespread showers and thunderstorms near these features, to the south of Wisconsin. Across southern Wisconsin, there is a chance for rain developing later Monday night, possibly mixed with sleet or snow along and north of a line from Port Washington to Portage and Reedsburg.
Mainly rain is expected most areas on Tuesday, but it will be a cold rain with temperatures remaining in the 30s. The rain will likely mix with or change over to sleet and snow Tuesday night. There may even be some freezing rain for a time Tuesday night.
Although precipitation appears to be likely, there is still quite a bit of uncertainty regarding the low level thermal structure of the atmosphere during this event. A slight shift southward in the low pressure track would result in colder air across southern Wisconsin, which would increase the accumulating snow risk. A slight shift to the north would result in more rain, and less of a wintery mix.
All interests will want to stay up-to-date on this return to cold temperatures and wintery weather on Tuesday and Tuesday night. Colder, below normal temperatures will then linger over the area for the later part of next week.