Thunderstorms developed along and ahead of a cold front as it encountered moist and unstable air across Wisconsin.
A record number of tornadoes for April struck Wisconsin on April 10.  Fifteen twisters affected the state as a strong spring storm moved across the western Great Lakes.  In the National Weather Service Green Bay service area of northeast Wisconsin, ten tornadoes were reported, a record single-day outbreak for any month of the year.
In addition to the tornadoes, the lines of thunderstorms that developed produced plenty of straight line wind damage and large hail.  Wind gusts, some estimated in the 80 mph to 100 mph range, downed numerous trees, damaged a small building, caused an injury and damage to two homes, toppled an 80-foot tall radio tower, threw a carport two houses away, and caused major damage to two industrial buildings.  The largest hail reported was baseball size near Winneconne in Winnebago County.

Hail in BROWN, WISCONSIN
From 10-APR-11 17:19:00 to 10-APR-11 17:19:00 (CST-6)
Location: NEW ROME
Magnitude: 1.00 
Reported by: Amateur Radio

Thunderstorms produced penny size hail that fell near New Rome.

Hail in KEWAUNEE, WISCONSIN
From 10-APR-11 15:37:00 to 10-APR-11 15:37:00 (CST-6)
Location: KEWAUNEE
Magnitude: 2.00 
Reported by: Fire Department/Rescue

Thunderstorms produced lime size hail that fell at Kewaunee.

Hail in KEWAUNEE, WISCONSIN
From 10-APR-11 15:33:00 to 10-APR-11 15:33:00 (CST-6)
Location: KEWAUNEE
Magnitude: 1.00 
Reported by: Amateur Radio

Thunderstorms produced penny size hail that fell at the intersection of 3rd Street and Ellis Street in Kewaunee.

Tornado in FLORENCE, WISCONSIN
From 10-APR-11 18:46:00 to 10-APR-11 18:51:00 (CST-6)
Location: LONG LAKE
Tornado F-scale: EF0
Property damage: 15.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

The tornado that formed near Argonne (Forest County) entered southwest Florence County at 7:46 pm CDT (1846 CST).  Several large tree branches were broken (DI 28, DOD 2) before the tornado dissipated at 7:51 pm CDT (1851 CST).  The average path width of the tornado in Florence County was 75 yards.

Tornado in FOREST, WISCONSIN
From 10-APR-11 19:03:00 to 10-APR-11 19:08:00 (CST-6)
Location: ARMSTRONG CREEK
Tornado F-scale: EF1
Property damage: 50.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A second tornado formed in Forest County about four miles west of Armstrong Creek at 8:03 pm CDT (1903 CST).  The tornado snapped and uprooted trees and damaged two houses.  One of the houses sustained significant roof damage (DI 2, DOD 4) as the tornado moved across the area.  The average width was 125 yards.

Hail in KEWAUNEE, WISCONSIN
From 10-APR-11 15:32:00 to 10-APR-11 15:32:00 (CST-6)
Location: KEWAUNEE
Magnitude: 1.00 
Reported by: Trained Spotter

Thunderstorms produced penny size hail that covered the ground a couple miles southwest of the city of Kewaunee.

Thunderstorm Wind in WAUSHARA, WISCONSIN
From 10-APR-11 18:40:00 to 10-APR-11 18:40:00 (CST-6)
Location: WILD ROSE
Magnitude: 52.00 EG
Reported by: Amateur Radio

Thunderstorms produced gusts to 60 mph along with penny size hail.

Hail in WAUSHARA, WISCONSIN
From 10-APR-11 17:42:00 to 10-APR-11 17:42:00 (CST-6)
Location: HANCOCK
Magnitude: 1.00 
Reported by: Trained Spotter

Thunderstorms produced quarter size hail that fell near the intersection of County Road C and Interstate 39.

Hail in OUTAGAMIE, WISCONSIN
From 10-APR-11 19:30:00 to 10-APR-11 19:30:00 (CST-6)
Location: GREENVILLE
Magnitude: 0.75 
Reported by: Trained Spotter

Thunderstorms produced penny size hail that fell near the intersection of State Highways 15 and 76.

Hail in KEWAUNEE, WISCONSIN
From 10-APR-11 15:32:00 to 10-APR-11 15:32:00 (CST-6)
Location: KEWAUNEE
Magnitude: 1.75 
Reported by: County Official

Thunderstorms produced golf ball size hail that fell in Kewaunee.

Hail in FOREST, WISCONSIN
From 10-APR-11 18:30:00 to 10-APR-11 18:30:00 (CST-6)
Location: ARGONNE
Magnitude: 1.25 
Reported by: COOP Observer

Thunderstorms produced half dollar size hail that fell north of Argonne.

Tornado in LANGLADE, WISCONSIN
From 10-APR-11 17:50:00 to 10-APR-11 17:58:00 (CST-6)
Location: PARRISH
Tornado F-scale: EF1
Property damage: 1.00M
Crop damage: 0.00K
Reported by: Park/Forest Service

A tornado formed about five miles south of Parrish at 6:50 pm CDT (1750 CST) and moved just east of north for a little over five miles.  The tornado affected about 1600 acres of hardwood and softwood trees.  It was estimated that over one million trees were snapped, uprooted, or suffered serious damage (DI 27, DOD 3-4).  The loss to timber alone is estimated at over one million dollars.  One cabin was destroyed by fallen trees.  The tornado was seen by a storm chaser at 6:55 pm CDT.  The average width of the tornado was 250 yards.

Tornado in WAUSHARA, WISCONSIN
From 10-APR-11 18:53:00 to 10-APR-11 19:04:00 (CST-6)
Location: POY SIPPI
Tornado F-scale: EF1
Property damage: 100.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A tornado formed near Poy Sippi, moved east-northeast over the north shore of Lake Poygan, then entered Winnebago County at 8:04 pm CDT (1904 CST).  The tornado damaged a house (DI 2, DOD 4) and destroyed a barn (DI 1, DOD 6) in the Poy Sippi area.  Another barn was flattened (DI 1, DOD 6) near the north shore of Lake Poygan. Many pine and fir trees were uprooted or snapped (DI 28, DOD 3-4) along the path of the storm.  The average path width was 100 yards.

Tornado in WINNEBAGO, WISCONSIN
From 10-APR-11 19:04:00 to 10-APR-11 19:07:00 (CST-6)
Location: LAKE POYGAN
Tornado F-scale: EF1
Property damage: 1.37M
Crop damage: 0.00K
Reported by: NWS Storm Survey

The tornado that formed near Poy Sippi crossed into Winnebago County at 8:04 pm CDT (1904 CST).  The tornado moved along the north shore of Lake Poygan, causing most of its damage near Boom Bay on the northeast shore.  Two homes were heavily damaged as portions of their roofs were partially ripped off (DI 2, DOD 4).  Several other houses sustained lesser damage in this area.  In addition, two small mobile homes were rolled on their side (DI 3, DOD 5) and many trees were uprooted or snapped.  The tornado dissipated about 2 miles west of Winchester, although damage occurred east and southeast of this location from straight-line thunderstorm winds.  The average path width was 100 yards.

Tornado in OUTAGAMIE, WISCONSIN
From 10-APR-11 19:43:00 to 10-APR-11 19:46:00 (CST-6)
Location: KAUKAUNA
Tornado F-scale: EF2
Property damage: 6.70M
Crop damage: 0.00K
Reported by: NWS Storm Survey

A fast moving tornado touched down in the southwest side of Kaukauna near County Road CE at 8:43 pm CDT (1743 CST).  The tornado cut through the center of a subdivision as it moved north-northeast to near the Fox River before lifting off the ground.  Seven homes were destroyed, 24 homes and four businesses sustained major damage, and 160 other homes sustained minor damage.  Several houses lost large sections of their roofs (DI 2, DOD 6) in the hardest hit area of the city.  The average path width was 125 yards.

Thunderstorm Wind in WAUSHARA, WISCONSIN
From 10-APR-11 17:54:00 to 10-APR-11 17:54:00 (CST-6)
Location: WAUTOMA
Magnitude: 78.00 EG
Reported by: Trained Spotter

Thunderstorm wind gusts of 80 to 90 mph downed 12-inch diameter trees in western Waushara County.

Thunderstorm Wind in WAUSHARA, WISCONSIN
From 10-APR-11 18:00:00 to 10-APR-11 18:00:00 (CST-6)
Location: WAUTOMA
Magnitude: 78.00 EG
Reported by: Storm Chaser

Thunderstorm wind gusts of 80 to 90 mph downed numerous trees north and northwest of Wautoma, including a 100-year-old oak tree.  Many trees were knocked down along Highway 73, some blocking the road.

Thunderstorm Wind in CALUMET, WISCONSIN
From 10-APR-11 20:01:00 to 10-APR-11 20:01:00 (CST-6)
Location: BRILLION
Magnitude: 52.00 EG
Reported by: Emergency Manager

Thunderstorm wind gusts of 50 to 60 mph downed power lines in Brillion.

Tornado in BROWN, WISCONSIN
From 10-APR-11 19:53:00 to 10-APR-11 19:55:00 (CST-6)
Location: ASKEATON
Tornado F-scale: EF1
Property damage: 15.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A brief tornado touched down about a mile and a half south of Greenleaf.  The tornado damaged the tops of two silos then ripped the roof off a barn (DI 1, DOD 5).  Average path width was 75 yards.

Thunderstorm Wind in WAUSHARA, WISCONSIN
From 10-APR-11 18:37:00 to 10-APR-11 18:37:00 (CST-6)
Location: WAUTOMA
Magnitude: 70.00 EG
Reported by: Trained Spotter

Thunderstorm wind gusts to 80 mph downed large trees about 4 miles north of Wautoma.

Thunderstorm Wind in OUTAGAMIE, WISCONSIN
From 10-APR-11 19:46:00 to 10-APR-11 19:46:00 (CST-6)
Location: APPLETON
Magnitude: 52.00 MG
Reported by: Amateur Radio

Thunderstorms southeast of Appleton produced a measured wind gust of 60 mph.

Tornado in CALUMET, WISCONSIN
From 10-APR-11 19:59:00 to 10-APR-11 20:01:00 (CST-6)
Location: QUINNEY
Tornado F-scale: EF1
Property damage: 100.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A brief tornado moved off Lake Winnebago and onshore south of Stockbridge just before 9:00 pm CDT (2000 CST).  The waterspout was seen as it moved onto the shore, damaging two homes.  A three-season room on one of the houses was ripped off the structure (DI 2, DOD 4).  The tornado moved northeast and tore off a section of the roof of a large outbuilding (DI 1, DOD 4).  The tops of trees were snapped in two areas along the path of the tornado.  The average path width was 75 yards.

Thunderstorm Wind in CALUMET, WISCONSIN
From 10-APR-11 20:06:00 to 10-APR-11 20:06:00 (CST-6)
Location: CHILTON
Magnitude: 56.00 MG
Reported by: Public

A school in Chilton measured a thunderstorm wind gust of 64 mph.

Thunderstorm Wind in MANITOWOC, WISCONSIN
From 10-APR-11 20:38:00 to 10-APR-11 20:38:00 (CST-6)
Location: MANITOWOC
Magnitude: 56.00 EG
Reported by: Public

Thunderstorms in Manitowoc produced estimated wind gusts to 65 mph.

Thunderstorm Wind in LANGLADE, WISCONSIN
From 10-APR-11 17:41:00 to 10-APR-11 17:41:00 (CST-6)
Location: DEERBROOK
Magnitude: 74.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Two houses sustained minor damage from straight line winds associated with a thunderstorm that, about 10 minutes later, produced a tornado near Parrish.  An occupant of one of the houses sustained minor injuries from flying glass.

Tornado in OUTAGAMIE, WISCONSIN
From 10-APR-11 18:32:00 to 10-APR-11 18:43:00 (CST-6)
Location: DALE
Tornado F-scale: EF1
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

The tornado that formed near Saxeville in Waushara County moved across southeast Waupaca County and into southwest Outagamie County at 7:32 pm CDT (1832 CST).  The tornado, which was not on the ground the entire time, damaged a couple of farm buildings just south of Hortonville before it dissipated.  One of the buildings lost part of its roof (DI 1, DOD 5).  The average path width was 100 yards.

Thunderstorm Wind in LANGLADE, WISCONSIN
From 10-APR-11 17:54:00 to 10-APR-11 17:54:00 (CST-6)
Location: ELCHO
Magnitude: 52.00 EG
Reported by: Broadcast Media

Thunderstorm wind gusts downed trees in Elcho.

Hail in WINNEBAGO, WISCONSIN
From 10-APR-11 19:11:00 to 10-APR-11 19:11:00 (CST-6)
Location: LAKE WINNECONNE
Magnitude: 2.75 
Reported by: Law Enforcement

Baseball size hail fell north of Winneconne on County Highway M.

Hail in WAUSHARA, WISCONSIN
From 10-APR-11 18:54:00 to 10-APR-11 18:54:00 (CST-6)
Location: PINE RIVER
Magnitude: 1.00 
Reported by: Trained Spotter

Quarter size hail fell at Pine River.

Hail in WAUSHARA, WISCONSIN
From 10-APR-11 18:50:00 to 10-APR-11 18:50:00 (CST-6)
Location: WILD ROSE
Magnitude: 1.75 
Reported by: Trained Spotter

Golf ball size hail fell 2 miles east of Wild Rose.

Thunderstorm Wind in MANITOWOC, WISCONSIN
From 10-APR-11 20:15:00 to 10-APR-11 20:15:00 (CST-6)
Location: REEDSVILLE
Magnitude: 65.00 EG
Reported by: Law Enforcement

Thunderstorm winds downed trees in Reedsville.

Thunderstorm Wind in BROWN, WISCONSIN
From 10-APR-11 19:48:00 to 10-APR-11 19:48:00 (CST-6)
Location: ASKEATON
Magnitude: 61.00 EG
Reported by: Law Enforcement

Thunderstorm winds damaged a small building on Country Road D.

Tornado in MARATHON, WISCONSIN
From 10-APR-11 17:08:00 to 10-APR-11 17:10:00 (CST-6)
Location: HAMBURG
Tornado F-scale: EF0
Property damage: 258.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A tornado developed about 2 miles north of Hamburg at 6:08 pm CDT (1708 CST) and moved northeast into Lincoln County at 6:10 pm CDT (1710 CST).  Pine trees were uprooted and large branches were broken in the path of the storm (DI 28, DOD 2-3).  A house sustained damage to its siding (DI 2, DOD 2) and several barns were blown down or lost their roofs (DI 1, DOD 2-3).  The average width of the tornado in Marathon County was 100 yards.  The tornado reached EF3 intensity in Lincoln County.

Tornado in LINCOLN, WISCONSIN
From 10-APR-11 17:10:00 to 10-APR-11 17:41:00 (CST-6)
Location: CORNING
Tornado F-scale: EF3
Property damage: 10.90M
Crop damage: 0.00K
Reported by: NWS Storm Survey

The tornado that formed north of Hamburg (Marathon County) at 6:08 pm CDT (1708 CST) moved into Lincoln County at 6:10 pm CDT (1710 CST).  The tornado reached EF3 intensity on the north side of Merrill at approximately 6:22 pm, where 22 homes and seven businesses were destroyed.  Several homes lost nearly all exterior and some interior walls (DI 2, DOD 7-8).  In addition, 22 homes and one business sustained major damage, and 20 home and four businesses sustained minor damage.  A 67 year old male was thrown over 200 feet from his bedroom and suffered broken ribs, a ruptured spleen, and a bruised lung.  Another person sustained minor injuries.  The tornado tore a path over 20 miles long in Lincoln County before dissipating.  The maximum width was about six tenths of a mile (1050 yards) wide.  The average width was about 400 yards.

Thunderstorm Wind in MANITOWOC, WISCONSIN
From 10-APR-11 20:57:00 to 10-APR-11 20:57:00 (CST-6)
Location: CLEVELAND
Magnitude: 61.00 EG
Reported by: Law Enforcement

Thunderstorm winds downed trees in Cleveland.

Hail in WAUSHARA, WISCONSIN
From 10-APR-11 18:40:00 to 10-APR-11 18:40:00 (CST-6)
Location: WILD ROSE
Magnitude: 0.75 
Reported by: Amateur Radio

Penny size hail fell east of Wild Rose and wind gusts reached 60 mph.

Hail in WAUSHARA, WISCONSIN
From 10-APR-11 18:35:00 to 10-APR-11 18:35:00 (CST-6)
Location: WAUTOMA
Magnitude: 1.75 
Reported by: Trained Spotter

Thunderstorms produced golf ball size hail that fell at Wautoma.

Hail in FOREST, WISCONSIN
From 10-APR-11 18:35:00 to 10-APR-11 18:35:00 (CST-6)
Location: ARGONNE
Magnitude: 1.75 
Reported by: Storm Chaser

Thunderstorms produced golf ball size hail that fell at Argonne.

Thunderstorm Wind in WINNEBAGO, WISCONSIN
From 10-APR-11 19:46:00 to 10-APR-11 19:46:00 (CST-6)
Location: FISK
Magnitude: 65.00 EG
Reported by: Trained Spotter

Thunderstorm wind gusts to 75 mph downed trees southwest of Oshkosh.

Funnel Cloud in OUTAGAMIE, WISCONSIN
From 10-APR-11 18:35:00 to 10-APR-11 18:35:00 (CST-6)
Location: DALE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

A ham radio operator spotted a funnel cloud near Dale in southwest Outagamie County.

Tornado in WAUSHARA, WISCONSIN
From 10-APR-11 17:35:00 to 10-APR-11 17:42:00 (CST-6)
Location: COLOMA MUNI ARPT
Tornado F-scale: EF1
Property damage: 175.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This tornado moved out of Adams County and entered Waushara County at 6:35 pm CDT (1735 CST) about 1.8 miles northwest of Coloma.  The worst damage occurred just inside the Waushara County line.  A mobile home roof was torn off (DI 3, DOD 4) and roof damage was noted to several homes (DI 2, DOD 4).  The average width was about 80 yards.

Hail in FOREST, WISCONSIN
From 10-APR-11 18:35:00 to 10-APR-11 18:35:00 (CST-6)
Location: LAKE METONGA
Magnitude: 2.00 
Reported by: Trained Spotter

Thunderstorms produced 2 inch diameter hail near Crandon.

Tornado in FOREST, WISCONSIN
From 10-APR-11 18:30:00 to 10-APR-11 18:46:00 (CST-6)
Location: ARGONNE
Tornado F-scale: EF2
Property damage: 200.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A tornado developed about 3.5 miles southeast of Argonne and moved northeast into Florence County.  The storm uprooted and snapped hundreds of trees, some of which fell on vacation cabins along the storm's path.  The hardest hit area was several miles east of Argonne shortly after the tornado developed.  A large part of the roof of a house was removed (DI 2, DOD 6).  The tornado continued northeast into Florence County at 7:46 pm CDT (1846 CST).  The average width of the tornado was 250 yards.

Thunderstorm Wind in WINNEBAGO, WISCONSIN
From 10-APR-11 19:30:00 to 10-APR-11 19:30:00 (CST-6)
Location: NEENAH
Magnitude: 87.00 EG
Property damage: 5.00M
Reported by: Trained Spotter

Thunderstorm downburst wind gusts, estimated in the 75 to 100 mph range, caused major damage to 2 large industrial buildings in the Neenah-Menasha area.  Much of the west-facing wall of one building was blow inward.  The high winds also downed trees and power lines, knocked down an 80-foot ham radio tower, bent a large flagpole, downed fences and threw a carport into a yard two houses down the street.

Hail in WINNEBAGO, WISCONSIN
From 10-APR-11 18:34:00 to 10-APR-11 18:34:00 (CST-6)
Location: WINCHESTER
Magnitude: 0.75 
Reported by: Amateur Radio

Thunderstorms produced penny size hail that fell west of Winchester.

Hail in PORTAGE, WISCONSIN
From 10-APR-11 17:57:00 to 10-APR-11 17:57:00 (CST-6)
Location: BLAINE
Magnitude: 0.75 
Reported by: Amateur Radio

Thunderstorms produced penny size hail that fell north of Wild Rose.

Funnel Cloud in WINNEBAGO, WISCONSIN
From 10-APR-11 19:20:00 to 10-APR-11 19:20:00 (CST-6)
Location: LAKE WINNECONNE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A funnel cloud was spotted on Oak Ridge Road in Winnebago County.

Funnel Cloud in BROWN, WISCONSIN
From 10-APR-11 20:15:00 to 10-APR-11 20:15:00 (CST-6)
Location: DENMARK
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A funnel cloud was spotted at Cooperstown Road near Denmark, in eastern Brown County.

Hail in WAUSHARA, WISCONSIN
From 10-APR-11 17:53:00 to 10-APR-11 17:53:00 (CST-6)
Location: WILD ROSE
Magnitude: 1.75 
Reported by: Amateur Radio

Thunderstorms produced golf ball size hail and a rotating wall cloud at Wild Rose.

Hail in PORTAGE, WISCONSIN
From 10-APR-11 17:51:00 to 10-APR-11 17:51:00 (CST-6)
Location: BANCROFT
Magnitude: 1.00 
Reported by: Storm Chaser

Thunderstorms produced penny size hail that fell around Almond near Interstate Highway 39.

Tornado in WAUSHARA, WISCONSIN
From 10-APR-11 18:06:00 to 10-APR-11 18:20:00 (CST-6)
Location: SAXEVILLE
Tornado F-scale: EF1
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A tornado developed at approximately 7:06 pm CDT (1806 CST) near Saxeville in Waushara County and moved east-northeast across east-central Wisconsin.  Numerous pine trees were snapped or uprooted (DI 28, DOD 4) near the initial point of contact.  As the tornado moved into West Bloomfield, several farm buildings were heavily damaged, including a barn that collapsed (DI 1, DOD 6).  The tornado had an average width of 100 yards, but it was not on the ground continuously.  The tornado entered Waupaca County at 7:20 pm CDT (1820 CST).

Tornado in WAUPACA, WISCONSIN
From 10-APR-11 18:20:00 to 10-APR-11 18:32:00 (CST-6)
Location: FREMONT
Tornado F-scale: EF1
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

The tornado that formed near Saxeville moved into Waupaca County at 7:20 pm CDT (1820 CST) southwest of Fremont.  Several farm buildings were impacted by the tornado in addition to many trees.  Near Readfield, a barn was lifted and rolled off its foundation (DI 1, DOD 7).  A poorly anchored house roof, which overhung the house walls, was completely removed with debris strewn nearly 1/4 mile to the northeast (DI 2, DOD 6; lower values).  The average width was 100 yards.  The tornado moved into Outagamie County at 7:32 pm CDT (1832 CST).