A round of showers and thunderstorms is expected tonight as a cold front and low pressure circulation pass through the region. The water vapor satellite image below was captured at 5 PM this Tuesday afternoon and shows the circulation over northern and central Minnesota. This circulation will take an east to southeast track across northern and central Wisconsin tonight. The best chance for thunderstorms will be tonight around and shortly after midnight, and continuing through about 4 am. There is a slight risk that some of the thunderstorms could become severe overnight, producing damaging wind gusts and large hail.
The image below shows a possible evolution of the storms overnight. There is more confidence in the timing of the storms rather than the exact form/shape these storms will take. Typically, the storms start out as descrete thunderstoms (like what is happening over northern Minnesota), then evolves into a larger complex of storms, often in the shape of a line.
While the chance of thunderstorms will linger into Wednesday, high pressure will move overhead for Thursday, bringing pleasant weather back to southern Wisconsin. See the graphic below for the forecast this week:
The images below show the local and regional radar loops. Click each image to go to the associated webpage.
The following images show the expected rainfall through Wednesday afternoon on a state scale and local scale. Click each image for a larger version.
National Weather Service - Milwaukee/Sullivan, WI