March 30, 2005: Hail and a tornado across six counties

An unusually early-season severe weather outbreak (first of the season), consisting of 3 rounds of widespread, severe storms, affected south-central and southeast Wisconsin on March 30, 2005. One brief tornado was documented, and there were numerous reports of large hail and damaging, straight-line, downburst, thunderstorm winds. Most of the larger hailstones consisted of clumps of soft hail of various sizes. The responsible surface low-pressure system developed in the Plains during the morning hours, and moved to northwest Wisconsin by the late evening hours. Meanwhile, an associated surface warm front surged north into central Wisconsin during the morning hours, bringing unseasonably warm air into the area. Maximum afternoon temperatures ranged from the upper 60s to mid 70s inland from Lake Michigan, with the highest reading of 77 in Janesville and 9NW Beloit.As instability increased during the morning, isolated thunderstorms developed across eastern part of the state of Iowa. These storms grew more intense and moved into south-central and southwest Wisconsin. The first round of severe thunderstorms occurred as an elongated supercell crossed the Illinois/Wisconsin border and into Lafayette and Iowa counties between 1130 and 1220CST. This storm produced .75 to 1.50 inch diameter hail before moving into Dane county where it split into two supercells. The northern most supercell briefly produced an F0 tornado just east of Waunakee. Both of these storms continued through Columbia, Dodge, and Fond du Lac counties where they produced funnel clouds, wind gusts to 56 knots (65 mph), and .75 to 1.25 inch diameter hail. As clouds began to decrease in the wake of these supercells, instability increased and scattered thunderstorms re-developed across south-central and southeast Wisconsin during the afternoon. These storms quickly pulsed to severe limits, producing wind gusts generally between 52 and 60 knots (60 to 70 mph) and 3/4 to 1 inch diameter hail. One thunderstorm's gust front produced a gustnado just northwest of St. Lawrence (Washington Co.) with estimated wind gusts to 65 knots (75 mph).The final round of severe thunderstorms (just ahead of a cold front) developed across northeast Illinois and pushed through southeast Wisconsin between 1700 and 1900CST. These storms produced 3/4 to 1 inch diameter hail, and wind gusts to around 52 knots (60 mph) across portions of Milwaukee, Waukesha, Walworth, Racine, and Kenosha counties. The damaging winds blew over a billboard in Kenosha county and parts of a roof and power lines were found on a roadway in Racine county.