From Meteorologist Tom Mahoney:
It is unusual but not out of the question. Snow in Wisconsin in May.
A Winter Weather Advisory will go into effect tonight in Northern Wisconsin from Oconto County northward. It will last until 7am tomorrow. While there may be 2"-4" of snow in the advisory area, there could also be up to 2" possible in Green Bay and the Fox Cities. The storm will exit tomorrow morning and will be followed by a sunny Mother's Day.