Storm Record · Columbia, Dane, Dodge, Jefferson, Sauk, Walworth, Waukesha Counties
August 20, 2010: Straight-line wind across seven counties
What the National Weather Service recorded
A short wave moving up the leading flank of an elongated large-scale trough that extended from the Upper Mississippi River Valley to the Central Plains provided large-scale lift for thunderstorm development over southern Wisconsin. A warm front extended across central Wisconsin back to surface low pressure over west-central Minnesota. This placed southern Wisconsin in a warm humid air mass, with temperatures in the 80's and dew points in the lower 70's producing CAPE values reaching 2000 J/kg. Deep-layer shear profiles were favorable for supercells as well as multicell line segments that produced damaging wind gusts. The thunderstorm winds caused widespread tree and power line damage. WE energies reported 23,000 customers were without power.
Source: NOAA Storm Events Database · episode 44532
Every report, in the Weather Service's words
Where It Hit
| Location | County | Hazard | Size | Report |
|---|---|---|---|---|
| Pewaukee (3 SE) | Waukesha | Wind | 64 mph wind | The peak thunderstorm wind gust of 65 mph (56 knots) measured by a trained spotter. |
| Pardeeville (5 N) | Columbia | Wind | 64 mph wind | The Columbia County emergency manager reported tree damage caused by thunderstorm wind gusts estimated at 56 knots (65 mph). |
| Stoughton | Dane | Wind | 58 mph wind | County sheriff deputies reported trees and power lines were blown down by the strong thunderstorm gusts. |
| Ft Atkinson | Jefferson | Wind | 58 mph wind | County sheriff deputies reported trees were blown down by the strong thunderstorm gusts. |
| Lake Mills (4 NW) | Jefferson | Wind | 58 mph wind | County sheriff deputies reported trees were blown down by the strong thunderstorm gusts. |
| Whitewater | Jefferson | Wind | 58 mph wind | County sheriff deputies reported trees were blown down in and around the city of Whitewater to just west of Palmyra by the strong thunderstorm gusts. The damage was produced by three separate storms that trained over the area. There was also urban flooding in Whitewater and Palmyra caused by 2 inches of rain that fell in 45 minutes. |
| La Valle (8 W) | Sauk | Wind | 58 mph wind | County sheriff deputies reported trees were blown down by the strong thunderstorm gusts. |
| Lowell | Dodge | Wind | 58 mph wind | County sheriff deputies reported trees were blown down in the Lowell area by the strong thunderstorm gusts. |
| Walworth (.5 SE) | Walworth | Wind | 58 mph wind | The Walworth County Emergency Manager reported a pole barn was partially damaged by thunderstorm winds estimated at 50 knots (58 mph). |
| Horicon | Dodge | Wind | 58 mph wind | County sheriff deputies reported trees were blown down by the strong thunderstorm gusts. |
| Stonebank | Waukesha | Wind | 58 mph wind | County sheriff deputies reported trees were blown down by the strong thunderstorm gusts. |
| Delavan (2 S) | Walworth | Wind | 58 mph wind | The Walworth County Emergency Manager reported tree damage caused by thunderstorm winds estimated at 50 knots (58 mph). |
| Oak Hill (3.66 NE) | Jefferson | Wind | 58 mph wind | The peak thunderstorm wind gust of 58 mph (50 knots) measured at the National Weather Service office southeast of Sullivan. |
Service areas this storm touched