Thunderstorms pounded southern Minnesota, portions of Wisconsin, eastern Iowa and northern Illinois Friday afternoon and evening with hail, high winds and driving downpours -- and were expanding into sections of the Chicago area late Friday evening. Doppler radar scans detected tornadic circulations, prompting tornado warnings north of Dubuque in sections of eastern Iowa and south of Platteville in southwest Wisconsin.
Trained spotters in Dubuque reported rapid rotation within a funnel cloud which hovered above the city around 6:30 p.m. Gusts of 65 m.p.h. hit the city a short time later -- while 70 m.p.h. winds and torrential downpours combined to knock out power to the National Weather Service Office in Davenport while flooding downtown streets there. Rockford was hit with 60 m.p.h. winds around 9:10 p.m. Reports of heavy rain were widespread: In just 45 minutes, 2.75" swamped Aurora, Iowa, while 1.10" of rain fell in 15 minutes in Freeport.
The storms, which produced nearly 11,000 cloud-to-ground lightning strokes from eastern Iowa into northwest Illinois in just 6 hours, were produced by thunderstorms towering as high as 54,000 feet where temperatures plummeted to 69 degrees below zero. Little wonder the storms were prolific hail producers. Hailstones the size of tennis balls -- 2.50" in diameter -- lambasted an area 2 miles northwest of Oneida in Iowa's Delaware County. The day's largest hailstones, measuring 4.25" in diameter (grapefruit size) pounded Winneshiek, Iowa. And hail was responsible for severe crop damage along U.S. Route 20 just west of Dubuque.
Trained spotters in Dubuque reported rapid rotation within a funnel cloud which hovered above the city around 6:30 p.m. Gusts of 65 m.p.h. hit the city a short time later -- while 70 m.p.h. winds and torrential downpours combined to knock out power to the National Weather Service Office in Davenport while flooding downtown streets there. Rockford was hit with 60 m.p.h. winds around 9:10 p.m. Reports of heavy rain were widespread: In just 45 minutes, 2.75" swamped Aurora, Iowa, while 1.10" of rain fell in 15 minutes in Freeport.
The storms, which produced nearly 11,000 cloud-to-ground lightning strokes from eastern Iowa into northwest Illinois in just 6 hours, were produced by thunderstorms towering as high as 54,000 feet where temperatures plummeted to 69 degrees below zero. Little wonder the storms were prolific hail producers. Hailstones the size of tennis balls -- 2.50" in diameter -- lambasted an area 2 miles northwest of Oneida in Iowa's Delaware County. The day's largest hailstones, measuring 4.25" in diameter (grapefruit size) pounded Winneshiek, Iowa. And hail was responsible for severe crop damage along U.S. Route 20 just west of Dubuque.
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