UPDATE 10:00AM - Flash flood warning issued for the Madison/Watertown area until 11:15AM
Radar estimated rainfall in excess of 5" between Madison and Milwaukee, generally north of I-94. Rain is just coming to an end now and there are spots at or above 6.0". Here are the official reports as of 9:45AM:
The Heavy Rain is driven by a slow moving anomalous 500mb low which provides convective instability and consistent source of organized lift across southern WI.