Flooding and Hail in Wisconsin, May 11 to 12, 2000

A second round of severe weather struck south-central and southeast Wisconsin overnight from the 11th into 12th. Some of the thunderstorms developed supercell characteristic resulting in large damaging hail, downburst straight-line winds, and torrential rainfalls. Nearly all of the severe storms in this round of activity leveled large trees and power lines. The worst damage was reported in the Allentown to West Bend area of Washington County, with two pole sheds and two residential garages sustaining considerable damage. Large hail up to golf ball size also occurred with the hurricane-force winds in Washington County. Milwaukee and Waukesha counties also experienced the same type of damage due to hurricane-force thunderstorm winds. Two Brookfield (Waukesha Co.) homes were damaged when large trees were pushed on them. In Cudahy (Milwaukee Co.), where a trained spotter's wind anemometer was blown away at 70 mph...the still-increasing winds pushed his home slightly off its foundation.Torrential rains coming down at the rate of 1 to 2 inches per hour in the more intense storms resulted in urban flooding as well. Many reports indicated that water was briefly 6 inches to almost 2 feet deep on some low-lying roads or underpasses. A peak rain of 3.6 inches in one hour was reported near the city of Racine! Due to the toppled power lines, about 25,000 customers were without power at one time or another. Synoptically, a warm front, that was over northern Illinois on the 11th, moved into southern Wisconsin during the overnight hours. This front served as a focus for the thunderstorm activity.