During the pre-dawn early morning hours of July 20th, a severe squall line pushed into south-central and southeast Wisconsin from southern Minnesota.  This squall line produced mainly damaging winds, some reports being "significant" (>65 knots or hurricane-force), and only a couple hail reports.  One of the significant reports was at a location 4 miles northeast of Monona at 0140CST where a gust of 71 knots (82 mph) was measured, before the power went out.  Hundreds of trees were knocked down in the Madison area, and there were dozens power-line damage reports.  Up to 40,000 customers lost electrical power across southern Wisconsin, with 13,000 alone in the Madison area.  The squall line weakened as it approached the corner of southeast Wisconsin due to weakening instability, despite still favorable deep layer shear.  Toward dawn, more scattered thunderstorms developed across south-central Wisconsin as a northwest to southeast axis of instability redeveloped.  A few of these storms pulsed up to produce only marginal severe hail and wind.

Thunderstorm Wind in JEFFERSON, WISCONSIN
From 20-JUL-06 01:58:00 to 20-JUL-06 01:58:00 (CST)
Location: WATERLOO
Magnitude: 56 EG
Property damage: 5K
Reported by: LAW ENFORCEMENT

Trees and power lines down.

Thunderstorm Wind in JEFFERSON, WISCONSIN
From 20-JUL-06 02:25:00 to 20-JUL-06 02:25:00 (CST)
Location: ROME
Magnitude: 56 EG
Reported by: LAW ENFORCEMENT

Tree down.

Lightning in ROCK, WISCONSIN
From 20-JUL-06 02:30:00 to 20-JUL-06 02:30:00 (CST)
Location: MILTON
Property damage: 50K
Reported by: NEWSPAPER

Lightning struck a barn, and the resultant fire burned the empty barn to the ground.

Lightning in SHEBOYGAN, WISCONSIN
From 20-JUL-06 04:30:00 to 20-JUL-06 04:30:00 (CST)
Location: BEECHWOOD
Property damage: 5K
Reported by: NEWSPAPER

Lightning struck a power-line voltage regulator, disrupting power to about 100 homes on CTH S.

Thunderstorm Wind in DANE, WISCONSIN
From 20-JUL-06 01:50:00 to 20-JUL-06 01:50:00 (CST)
Location: ALBION
Magnitude: 56 EG
Property damage: 2K
Reported by: NEWSPAPER

Trees down.  One large tree fell on a home's roof, resulting in minor damage.

Hail in DANE, WISCONSIN
From 20-JUL-06 01:34:00 to 20-JUL-06 01:40:00 (CST)
Location: MADISON
Magnitude: 0.75 
Reported by: TRAINED SPOTTER

Thunderstorm Wind in IOWA, WISCONSIN
From 20-JUL-06 01:05:00 to 20-JUL-06 01:25:00 (CST)
Location: AVOCA
Magnitude: 65 EG
Property damage: 50K
Reported by: LAW ENFORCEMENT

Trees and power lines reported down countywide.

Thunderstorm Wind in WAUKESHA, WISCONSIN
From 20-JUL-06 02:30:00 to 20-JUL-06 02:30:00 (CST)
Location: DOUSMAN
Magnitude: 52 EG
Reported by: NWS EMPLOYEE(OFF DUTY)

Tree limbs and trees down.

Thunderstorm Wind in WAUKESHA, WISCONSIN
From 20-JUL-06 02:40:00 to 20-JUL-06 02:40:00 (CST)
Location: BROOKFIELD
Magnitude: 52 EG
Property damage: 10K
Reported by: LAW ENFORCEMENT

Power lines down.

Thunderstorm Wind in DANE, WISCONSIN
From 20-JUL-06 02:00:00 to 20-JUL-06 02:00:00 (CST)
Location: BELLEVILLE
Magnitude: 52 EG
Property damage: 5K
Reported by: TRAINED SPOTTER

Large tree branches and power lines down.

Thunderstorm Wind in WALWORTH, WISCONSIN
From 20-JUL-06 02:35:00 to 20-JUL-06 02:42:00 (CST)
Location: DARIEN
Magnitude: 52 EG
Property damage: 10K
Reported by: LAW ENFORCEMENT

Trees and power lines down.

Hail in COLUMBIA, WISCONSIN
From 20-JUL-06 00:30:00 to 20-JUL-06 00:30:00 (CST)
Location: PARDEEVILLE
Magnitude: 0.88 
Reported by: TRAINED SPOTTER

Thunderstorm Wind in DANE, WISCONSIN
From 20-JUL-06 01:40:00 to 20-JUL-06 01:40:00 (CST)
Location: SUN PRAIRIE
Magnitude: 52 EG
Reported by: COOP STATION

Trees down.

Thunderstorm Wind in GREEN, WISCONSIN
From 20-JUL-06 02:10:00 to 20-JUL-06 02:10:00 (CST)
Location: DAYTON
Magnitude: 65 EG
Property damage: 10K
Reported by: LAW ENFORCEMENT

Strong winds at minimum hurricane-force caused trees to topple onto roads.  Some power-lines down.  Some cars then crashed into fallen trees in Brooklyn.

Thunderstorm Wind in DODGE, WISCONSIN
From 20-JUL-06 02:00:00 to 20-JUL-06 02:00:00 (CST)
Location: THERESA
Magnitude: 52 EG
Reported by: TRAINED SPOTTER

Trees down.

Lightning in RACINE, WISCONSIN
From 20-JUL-06 03:30:00 to 20-JUL-06 03:30:00 (CST)
Location: STURTEVANT
Property damage: 10K
Reported by: NEWSPAPER

Lightning struck a home in the 3200 block of 90th St., resulting in a roof fire.

Lightning in FOND DU LAC, WISCONSIN
From 20-JUL-06 07:04:00 to 20-JUL-06 07:04:00 (CST)
Location: ELMORE
Property damage: 80K
Reported by: NEWSPAPER

Lightning struck a rural home and the resultant fire burned the house to the ground.

Thunderstorm Wind in GREEN, WISCONSIN
From 20-JUL-06 02:10:00 to 20-JUL-06 02:12:00 (CST)
Location: ALBANY
Magnitude: 56 EG
Property damage: 20K
Reported by: TRAINED SPOTTER

Trees, power lines, and antennas down.  One large tree fell onto a vehicle in Brodhead, resulting in minor damage.

Hail in GREEN, WISCONSIN
From 20-JUL-06 05:42:00 to 20-JUL-06 05:42:00 (CST)
Location: ALBANY
Magnitude: 0.75 
Reported by: TRAINED SPOTTER

Lightning in RACINE, WISCONSIN
From 20-JUL-06 04:30:00 to 20-JUL-06 04:30:00 (CST)
Location: RACINE
Property damage: 10K
Reported by: NEWSPAPER

Lightning struck a home on in the 1600 block of Edgewood Ave., resulting in a roof fire.

Thunderstorm Wind in DANE, WISCONSIN
From 20-JUL-06 01:35:00 to 20-JUL-06 01:40:00 (CST)
Location: BLUE MOUNDS
Magnitude: 56 EG
Property damage: 10K
Reported by: AMATEUR RADIO

Trees and power-lines down.

Thunderstorm Wind in DANE, WISCONSIN
From 20-JUL-06 01:40:00 to 20-JUL-06 01:40:00 (CST)
Location: MONONA
Magnitude: 71 MG
Property damage: 15K
Reported by: TRAINED SPOTTER

Hurricane force wind gusts to 71 knots (82 mph) produced tree and power line damage 4.0 miles northeast of Monona.

Thunderstorm Wind in LAFAYETTE, WISCONSIN
From 20-JUL-06 01:25:00 to 20-JUL-06 01:25:00 (CST)
Location: BELMONT
Magnitude: 65 EG
Property damage: 5K
Reported by: LAW ENFORCEMENT

Trees and power lines down.

Thunderstorm Wind in GREEN, WISCONSIN
From 20-JUL-06 05:23:00 to 20-JUL-06 05:23:00 (CST)
Location: NEW GLARUS
Magnitude: 52 EG
Reported by: TRAINED SPOTTER

Trees down.

Thunderstorm Wind in JEFFERSON, WISCONSIN
From 20-JUL-06 02:18:00 to 20-JUL-06 02:18:00 (CST)
Location: FT ATKINSON
Magnitude: 56 EG
Property damage: 25K
Reported by: LAW ENFORCEMENT

Trees toppled over.  Two small planes at the Ft. Atkinson Municipal Airport broke loose from their morrings due to the powerful winds.  One of the plane's wings were damaged as it tipped from side to side.

Thunderstorm Wind in GREEN, WISCONSIN
From 20-JUL-06 01:45:00 to 20-JUL-06 01:45:00 (CST)
Location: NEW GLARUS
Magnitude: 65 EG
Property damage: 10K
Reported by: LAW ENFORCEMENT

A car was crushed and a truck's window was broken by falling trees.  Antennas also damaged.

Thunderstorm Wind in DANE, WISCONSIN
From 20-JUL-06 05:14:00 to 20-JUL-06 05:14:00 (CST)
Location: BLUE MOUNDS
Magnitude: 52 EG
Reported by: TRAINED SPOTTER

Tree and tree branches down.

Thunderstorm Wind in COLUMBIA, WISCONSIN
From 20-JUL-06 01:09:00 to 20-JUL-06 01:18:00 (CST)
Location: PORTAGE
Magnitude: 56 EG
Property damage: 10K
Reported by: AMATEUR RADIO

Trees toppled and some power-lines downed.

Thunderstorm Wind in KENOSHA, WISCONSIN
From 20-JUL-06 03:10:00 to 20-JUL-06 03:10:00 (CST)
Location: PADDOCK LAKE
Magnitude: 52 EG
Property damage: 10K
Reported by: LAW ENFORCEMENT

Trees and tree branches fell onto power lines.

Thunderstorm Wind in RACINE, WISCONSIN
From 20-JUL-06 02:55:00 to 20-JUL-06 02:55:00 (CST)
Location: BURLINGTON
Magnitude: 52 EG
Property damage: 10K
Reported by: LAW ENFORCEMENT

Trees and power lines down.

Thunderstorm Wind in DODGE, WISCONSIN
From 20-JUL-06 01:57:00 to 20-JUL-06 01:57:00 (CST)
Location: PORTLAND
Magnitude: 56 EG
Property damage: 5K
Reported by: LAW ENFORCEMENT

Trees and power lines down.

Thunderstorm Wind in LAFAYETTE, WISCONSIN
From 20-JUL-06 01:45:00 to 20-JUL-06 01:45:00 (CST)
Location: SHULLSBURG
Magnitude: 65 EG
Property damage: 5K
Reported by: LAW ENFORCEMENT

Trees and power lines down.

Thunderstorm Wind in WALWORTH, WISCONSIN
From 20-JUL-06 02:50:00 to 20-JUL-06 02:50:00 (CST)
Location: LAKE GENEVA
Magnitude: 52 EG
Property damage: 5K
Reported by: LAW ENFORCEMENT

Trees and power lines down.

Thunderstorm Wind in WASHINGTON, WISCONSIN
From 20-JUL-06 02:30:00 to 20-JUL-06 02:30:00 (CST)
Location: RICHFIELD
Magnitude: 56 EG
Property damage: 5K
Reported by: LAW ENFORCEMENT

Trees and power lines down.

Lightning in MILWAUKEE, WISCONSIN
From 20-JUL-06 04:00:00 to 20-JUL-06 04:00:00 (CST)
Location: MILWAUKEE
Property damage: 15K
Reported by: NEWSPAPER

Lightning struck a home in the 1800 block of W. Greenfield Ave., resulting in a roof fire.

Thunderstorm Wind in LAFAYETTE, WISCONSIN
From 20-JUL-06 01:32:00 to 20-JUL-06 01:35:00 (CST)
Location: ARGYLE
Magnitude: 65 EG
Property damage: 20K
Reported by: LAW ENFORCEMENT

Trees and power lines down.

Thunderstorm Wind in DANE, WISCONSIN
From 20-JUL-06 01:25:00 to 20-JUL-06 01:45:00 (CST)
Location: MADISON
Magnitude: 65 EG
Property damage: 150K
Reported by: TRAINED SPOTTER

Bricks were taken off a building in downtown Madison due to severe, hurricane-force wind gusts to an estimated 65 knots (75 mph).  Dozens of power-lines were damaged.  At least 3 vehicles were either damaged or destroyed by fallen trees.  Many roads were blocked by the tree debris.  A large tree was toppled onto a home on the near east side of Madison, resulting in minor roof damage.

Thunderstorm Wind in SAUK, WISCONSIN
From 20-JUL-06 01:05:00 to 20-JUL-06 01:20:00 (CST)
Location: LA VALLE
Magnitude: 65 EG
Property damage: 50K
Reported by: LAW ENFORCEMENT

Trees and power lines reported down countywide.

Thunderstorm Wind in ROCK, WISCONSIN
From 20-JUL-06 01:55:00 to 20-JUL-06 02:25:00 (CST)
Location: UNION
Magnitude: 56 EG
Property damage: 75K
Reported by: LAW ENFORCEMENT

Trees and power lines down in a large swath from northwestern to southeastern Rock County.  In the city of Janesville, at least 3 cars were damaged by felled trees or tree branch debris. Several roads were temporarily blocked by tree debris.

Thunderstorm Wind in COLUMBIA, WISCONSIN
From 20-JUL-06 01:27:00 to 20-JUL-06 01:27:00 (CST)
Location: PARDEEVILLE
Magnitude: 56 EG
Reported by: AMATEUR RADIO

Thunderstorm Wind in COLUMBIA, WISCONSIN
From 20-JUL-06 01:30:00 to 20-JUL-06 01:30:00 (CST)
Location: WISCONSIN DELLS
Magnitude: 52 EG
Reported by: LAW ENFORCEMENT

Lightning in ROCK, WISCONSIN
From 20-JUL-06 02:25:00 to 20-JUL-06 02:25:00 (CST)
Location: MILTON
Property damage: 15K
Reported by: FIRE DEPT/RESCUE SQUAD

Lightning struck a barn causing it to catch fire.