Storm Record · Columbia, Dane, Dodge, Jefferson, Sauk, Walworth, Waukesha Counties
September 4, 2012: Straight-line wind across seven counties
What the National Weather Service recorded
Thunderstorms developed in the early evening of September 4th in an unstable air mass over the region with lift from an upper-level disturbance that moved across the western Great Lakes region ahead of a stronger wave in the Northern Plains. CAPE values of 2000 J/kg to 2500 J/kg and 0-6 km bulk shear around 30 knots was sufficient to produce favorable conditions for sustained updrafts. These factors produced clusters of severe thunderstorms that developed along a weak convergent boundary that extended from northeast Minnesota through western Wisconsin. The clusters of supercell thunderstorms produced damaging wind gusts over a good portion of South-Central and Southeast Wisconsin.
Source: NOAA Storm Events Database · episode 68874
Every report, in the Weather Service's words
Where It Hit
| Location | County | Hazard | Size | Report |
|---|---|---|---|---|
| Stoughton (2 SSW) | Dane | Wind | 64 mph wind | A HAM radio operator reported trees and large branches were blown down by damaging thunderstorm wind gusts estimated to be 56 knots (65 mph) 2 miles south-southwest of Stoughton. |
| Lake Mills | Jefferson | Wind | 64 mph wind | The Jefferson County 911 Call Center reported trees and power lines were blown down by damaging thunderstorm wind gusts estimated to be 56 knots (64 mph) in Lake Mills. |
| Stoughton (1 NE) | Dane | Wind | 64 mph wind | A trained spotter reported trees were blown down by damaging thunderstorm wind gusts estimated to be 56 knots (65 mph) 1 mile northeast of Stoughton. |
| Sun Prairie (2 W) | Dane | Wind | 64 mph wind | The public reported trees were blown down by damaging thunderstorm wind gusts estimated at 56 knots (65 mph) 2 miles west of Sun Prairie. |
| Portage | Columbia | Wind | 64 mph wind | Law enforcement officials reported trees were blown down by damaging thunderstorm wind gusts estimated at 56 knots (65 mph) in an 5-mile wide swath from Portage to Pardeeville. |
| La Grange | Walworth | Wind | 64 mph wind | The Walworth County 911 Center received reports of trees blown down by damaging thunderstorm wind gusts estimated at 56 knots (65 mph) from La Grange to Delavan. |
| Eagle (5 NW) | Waukesha | Wind | 64 mph wind | The Waukesha County 911 Center received reports of trees blown down by damaging thunderstorm wind gusts estimated at 56 knots (65 mph) from 5 miles northwest of Eagle to Eagle. |
| Baraboo (5 SE) | Sauk | Wind | 64 mph wind | Sauk County 911 Call Center personnel reported trees and power lines were blown down by damaging thunderstorm wind gusts estimated at 56 knots (65 mph) along a path from 5 miles southeast of Baraboo to Merrimac. |
| Rock Spgs (3 S) | Sauk | Wind | 64 mph wind | Sauk County 911 Call Center personnel reported trees and power lines were blown down by damaging thunderstorm wind gusts estimated at 56 knots (65 mph) along a path from 3 miles south of Rock Springs to 5 miles south-southwest of Baraboo. |
| Okee (4.1 NE) | Columbia | Wind | 64 mph wind | Law enforcement officials reported trees and power lines were blown down by damaging thunderstorm wind gusts estimated at 56 knots (65 mph) in an 8-mile wide swath from Harmony Grove to 5 miles east-southeast of Arlington. |
| Ft Atkinson (1 E) | Jefferson | Wind | 60 mph wind | A trained spotter reported trees were blown down by damaging thunderstorm wind gusts estimated to be 52 knots (60 mph) 1 mile east of Fort Atkinson. |
| Camp Randall Stadium (1 NE) | Dane | Wind | 60 mph wind | The public reported large tree branches were blown down by damaging thunderstorm wind gusts estimated at 50 knots (60 mph) 1 mile northeast of Camp Randall Stadium in Madison. |
| Lowell | Dodge | Wind | 60 mph wind | A trained spotter reported trees and power lines blown down by damaging thunderstorm wind gusts estimated at 52 knots (60 mph) in Lowell. |
| (msn)truax Fld Madis | Dane | Wind | 58 mph wind |
Service areas this storm touched