Thunderstorms with Heavy Freezing Rain Hit Central and East-Central Wisconsin

Last updated 4/10/13  12 pm

A strong storm system moved into Wisconsin and produced a six-hour period of heavy freezing rain and mixed precipitation during the early morning hours of April 10, 2013. The same system produced severe thunderstorms across Iowa and southeast Minnesota earlier in the evening of April 9.

One quarter to one-half inch of ice accumulated on trees and powerlines in central and east-central Wisconsin. As a result, tens of thousands of people were without power during the height of the storm as trees and powerlines buckled under the weight of the ice. At least one home was damaged by a fallen tree in the Oshkosh area. 

The freezing rain fell quite heavily between about midnight and 3 AM and was accompanied by cloud-to-ground lightning strikes, sleet, hail, and large snow flakes. As much as 3 inches of snow fell just northwest of Green Bay.

Here's a Wisconsin radar mosaic showing the large area of heavy precipitation across central and eastern Wisconsin at 2 AM:

Initially, mainly rain was expected, as temperatures were in the mid 30s. But a shallow layer of dry air funneling in from Canada caused the air over Wisconsin to cool rapidly as the precipitation began (from evaporative cooling). This allowed air temperatures to drop to just below freezing, which resulted in rain that froze to surfaces near the ground. The cold layer became deep enough near Green Bay and areas to the north for more snow than ice to fall there. is the U.S. government's official web portal to all federal, state and local government web resources and services.