F3 Tornado — Fond Du Lac, Wisconsin

2004-06-23 · near Alto, Fond Du Lac, Wisconsin

Event narrative

This tornado was a continuation of the tornado that moved east from the Lake Maria area of extreme southeastern Green Lake County. It maintained its F3 strength (175-200 mph) and moved east along Marshview Rd, only to merge with the F3 tornado moving east/southeast out of the Markesan area of southeast Green Lake County. The merger took place just east of a dogleg/bend of Oak Grove Rd., about 2.2 miles SSW of Alto. The civil Town of Alto reported that 8 residential homes had major damage. Four farms were affected with a tally of 8 ag-buildings/homes with minor damage, 19 with major damage, and 16 destroyed. Crop damage was severe. Public sector damage (roads/bridges) was about $100K. Average path width was about 275 yards.

Wider weather episode

Two rounds of severe weather affected parts of south-central and southeast Wisconsin on June 23rd, with the second round featuring 8 tornadoes, large hail (up to golf-ball size), and powerful straight-line downburst winds. A warm front moving north through the area resulted in favorable vertical wind shear to allow for supercell development.The 1st round of severe weather was due to a broken line of intense thunderstorms moving across Walworth, Milwaukee, Racine and Kenosha counties. Hail of up to 1 inch in diameter and torrential rainfall accompanied these storms before they moved over Lake Michigan and weakened. The 2nd round of severe weather was dominated by 2 cyclic supercells - one moved east/southeast through Marquette, Green Lake, Fond du Lac, and Washington Counties, spinning up 5 separate tornadoes, dumping hail stones up to 3 inches in diameter, and hurricane-force downburst winds. The large hail dented several vehicles. Two of these were rated F3. Refer to the individual tornado reports for more details. A more southerly supercell tracked across extreme southern Sauk County and then made a partial right turn and headed southeast through Dane County, spinning up 2 tornadoes in the process, as well as large hail and downburst winds. One powerful downburst wind in Madison (Dane Co.) blew equipment off the roof of a business at the Midvale Shopping Mall. A semi southwest of Ft. Atkinson was blown over by straight-line wind gusts. This southern supercell eventually spun up another tornado in south-central Jefferson County which moved into north-central Walworth County. Refer to the individual tornado reports for more details.Both supercells had downbursts that generated large hail and powerful, hurricane-force winds north and south of their tracks. Over all of Wisconsin, 16 tornadoes were documented on June 23rd, which is the 4th highest single-day total (record is 24 on May 8, 1988). For south-central and southeast Wisconsin, the 8 tornadoes on June 23rd was tied for the 4th highest single-day total (record is 11 on May 8, 1988).

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Source: NOAA Storm Events Database, event_id 5406515. Narrative written by the NWS forecast office that issued the report.