Heavy to excessive rainfall may lead to flooding Wednesday over southwest Pennsylvania into northern West Virginia, and western Maryland. Flood Watches have been issued. An extended period of hot weather will continue for parts of coastal southern California including Los Angeles through Thursday. Heat Advisories remain in effect. Read More >
Overview
During the early morning of August 28, 2007, a mesoscale convective system (MCS) moved over the southern Twin Cities metro area and into western Wisconsin. This MCS was first associated with marginal severe hail, but soon transitioned to a damaging wind event from Redwood Falls, Minnesota to Cornell, Wisconsin. Wind gusts of 60-70 miles per hour were observed in Redwood County, Carver County, and the Twin Cities metro area.Wind & Hail:
From midnight through 1 am, the thunderstorms appeared to have mainly a hail threat from north of the Twin Cities into western Wisconsin. Ping pong to golf ball size hail was observed in Chisago County for one storm. At 1:23 am, Redwood Falls reported wind gusts of 62 miles per hour. Low radar scans began to show velocity values of 60-70 knots near Carver County. Later, 82 knots was observed just under 500 feet in central Carver County. The bow structure of the MCS then moved east towards the Minneapolis Airport, which gusted to 71 miles per hour. St. Paul experienced wind gusts of 60 miles per hour. Radar signatures of very strong winds started to dissipate near Washington County, and then reappeared in western Wisconsin. The wind gusts caused significant damage to trees, power lines, cars, and some roof damage.Photos
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| Tree uprooted by wind in Waconia |
Car damage in Edina |
Tree damage in Waconia |
Radar:
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| High reflectivity showed strong storms | MCS bow structure moved east | MCS bow structure near Twin Cities | Storm relative velocity loop |
Storm Reports
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Environment
Elevated lapse rates and the intensity of the low-level jet (40-50 knots) provided ideal conditions for severe weather. Increasing southerly surface winds in southern Minnesota and 0-1 km shear around 10-15 knots also created a favorable environment. The soundings showed an abrupt change in lower level wind speed and direction throughout the early morning.
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| LAPS sounding at 6Z | LAPS sounding at 7Z | LAPS sounding at 8Z |
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| 250 mb 0Z analysis | Storm environment diagram |
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