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.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS GRB wrote it up.
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.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Green Bay, WI wrote its last area forecast discussion before the first event at Apr 10, 1:40 PM CST, 1 hour 52 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREEN BAY WI 240 PM CDT SUN APR 10 2011 .SHORT TERM...TNGT AND MON. MAIN FCST FOCUS TO BE ON SEVERE POTENTIAL LATE THIS AFTERNOON INTO THE EVENING HOURS. POTENTIAL EXISTS FOR SIGNIFICANT THUNDERSTORMS WITH DAMAGING WINDS...LARGE HAIL AND SEVERAL TORNADOES. THE 19Z MSAS SFC ANALYSIS SHOWED A STG AREA OF LOW PRES SITUATED OVER E-CNTRL MN WITH A WRMFNT EXTENDED EWD THRU CNTRL WI. A CDFNT STRETCHED SOUTH FROM THE LOW THRU CNTRL SECTIONS IA. AIR MASS ACROSS SRN WI HAS BECOME VERY UNSTABLE WITH DEW PTS RISING INTO THE LWR 60S...CAPES APPROACHING 2K J/KG AND LI'S AS LOW AS -8. RADAR MOSAIC/SATL IMAGERY INDICATED ACCAS CLDS/SCT SHWRS DEVELOPING OVER NE IA AND MOVING NEWD INTO CNTRL WI. NONE OF THESE STORMS ARE SVR AS OF YET. OUTBREAK OF SVR STORMS IS STILL EXPECTED LATE THIS AFTERNOON INTO THE EVENING HOURS OVER MUCH OF NE WI. THUNDERSTORMS ARE FCST TO DVLP FROM ERN MN/NE IA AHD OF THE CDFNT THIS AFTERNOON AND THEN MOVE RAPIDLY EAST (40 TO 50 MPH) THRU WI. THERMODYNAMICS ALL APR FAVORABLE FOR THESE STORMS TO QUICKLY TURN SEVERE AS JET ENERGY LIFTS NE THRU THE MIDWEST AHD OF THE MAIN UPR TROF. THESE SVR STORMS WL REACH CNTRL WI BETWEEN 5 AND 7 PM...ERN WI BETWEEN 7 AND 9 PM. LARGEST HODOGRAPHS ARE FCST TO RESIDE NEAR THE WRMFNT WHICH SHOULD BE LOCATED OVER NRN WI WHEN THE STORMS ARRIVE. THIS AREA WOULD HAVE THE BEST CHC OF SEEING TORNADO ACTIVITY WITH THE POSSIBILITY OF LONG-TRACKED TORNADOES. ANTICIPATE A WEATHER WATCH TO BE ISSUED SHORTLY. THE SFC LOW TO CONT MOVING NE THRU THE WRN GREAT LKS TNGT AND SWEEP THE CDFNT THRU THE FCST AREA THIS EVENING. ONGOING CONVECTION SHOULD ALREADY BE IN THE PROCESS OF EXITING WI AROUND THE MIDNGT HOUR WITH ONLY LGT STRATIFORM RAIN IN SCT FASHION FOR THE OVERNIGHT PERIOD. WINDS WL VEER WEST AND INCREASE THRU THE NGT WITH GUST APPROACHING 30 MPH TOWARD DAYBREAK. HAVE LOWERED MIN TEMPS A FEW DEGS AS COOLER AIR QUICKLY MOVES IN BEHIND THE DEPARTED CDFNT. WRAP-AROUND MSTR/SECONDARY SFC TROF/PASSAGE OF THE UPR TROF TO MOVE THRU WI MON MORNING AND MAY BE ABLE TO KICK OFF A FEW LGT SHWRS. BY MON AFTERNOON...A RDG OF HI PRES IS FCST TO MOVE INTO THE UPR MS VALLEY AND BEGIN TO ADVECT DRIER AIR INTO WI. HAVE LEFT A TOKEN SLGT CHC POP FOR THE AFTERNOON...BUT THESE MAY BE ABLE TO GET DROPPED IF MDLS PERSIST ON AMT OF DRYING. MAX TEMPS BACK TO NORMAL ON MON WITH LWR 50S NORTH...MID-UPR 50S ELSEWHERE. .LONG TERM...MONDAY NIGHT THROUGH SATURDAY. UPPER RIDGE BUILDS INTO THE AREA MONDAY NIGHT AND REMAINS ACROSS WISCONSIN BEFORE FLATTENING TUESDAY NIGHT. THIS SHOULD PROVIDE FOR DRY AND SEASONABLE WEATHER THROUGH EARLY WEDNESDAY. CLIPPER LIKE SYSTEM APPROACHES WEDNESDAY WITH A SURFACE COLD FRONT THAT DROPS ACROSS WISCONSIN BEFORE STALLING ACROSS NORTHERN ILLINOIS WEDNESDAY NIGHT THROUGH THURSDAY. THEN MODELS SUGGEST THAT AN INVERTED TROUGH WILL FORM FROM THE SOUTHERN PLAINS TO IOWA...WITH OVERRUNNING PRECIPITATION TO IT/S NORTH. UPPER JET ENERGY MOVING INTO THE SOUTHERN PLAINS FROM THE WESTERN UNITED STATES IS EXPECTED TO PRODUCE A CLOSED LOW OVER THE MID MISSISSIPPI VALLEY THURSDAY NIGHT WHICH THEN MOVES VERY SLOWLY EAST TO THE OHIO VALLEY BY SATURDAY. THE GFS IS FURTHER SOUTH THAN THE ECMWF AT FIRST BUT THEN THE TWO MODELS COME TOGETHER WITH A LOW OVER ILLINOIS ON SATURDAY. THIS COULD MAKE FOR AN EXTENDED PERIOD OF CLOUDS AND COOLER WEATHER THURSDAY THROUGH SATURDAY WITH PERIODS OF RAIN AND POSSIBLY SOME SNOW. ACCUMULATING SNOW POSSIBLE FRIDAY NIGHT AND SATURDAY IF THE BOUNDARY LAYER TEMPERATURES ARE COLD ENOUGH. && .AVIATION...VFR CONDITIONS TO ONLY LAST INTO THE EVENING HOURS BEFORE A CDFNT SWEEPS THRU THE RGN AND BRING SVR TSTMS TO MUCH OF THE AREA. SOUTH WNDS TO VEER WEST AND INCREASE INTO THE 15 TO 25 KT RANGE WITH GUSTS APPROACHING 30 KTS. A LARGE AREA OF LOW STRATUS CLDS TO THEN OVERSPREAD THE TAF SITES AFTER MIDNIGHT WITH CIGS/VSBYS IN THE IFR/MVFR RANGE. AS A RDG OF HI PRES BEGINS TO BUILD INTO THE WRN GREAT LKS MON AFTERNOON...EXPECT CIGS TO RETURN TO VFR CONDITIONS. && .GRB WATCHES/WARNINGS/ADVISORIES... FLOOD WATCH UNTIL 1 AM CDT MONDAY FOR WIZ018>021-030-031-035>040- 045-048>050-074. && KALLAS/RDM
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE GREEN BAY WI 1154 AM CDT SUN APR 10 2011 WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-111700- VILAS-ONEIDA-FOREST-FLORENCE-NORTHERN MARINETTE-LINCOLN-LANGLADE- MENOMINEE-NORTHERN OCONTO-DOOR-MARATHON-SHAWANO-WOOD-PORTAGE- WAUPACA-OUTAGAMIE-BROWN-KEWAUNEE-WAUSHARA-WINNEBAGO-CALUMET- MANITOWOC-SOUTHERN MARINETTE-SOUTHERN OCONTO- 1154 AM CDT SUN APR 10 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL AND NORTHEAST WISCONSIN. .DAY ONE...THIS AFTERNOON AND TONIGHT THERE IS A MODERATE RISK FOR SEVERE WEATHER OVER ALL OF NORTH CENTRAL AND NORTHEAST WISCONSIN THIS AFTERNOON AND EVENING. A MAJOR SEVERE WEATHER OUTBREAK STILL LOOKS LIKELY FOR LATE THIS AFTERNOON AND EVENING AS A STRONG LOW PRESSURE SYSTEM AND COLD FRONT MOVE INTO THE REGION. THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS WESTERN WISCONSIN AND NORTHEAST IOWA BY MID-AFTERNOON AND QUICKLY BECOME SEVERE. THESE SEVERE STORMS WILL RAPIDLY SWEEP EAST AT 40 TO 50 MPH ACROSS CENTRAL AND EASTERN WISCONSIN BETWEEN 5 AND 9 PM WITH THE PRIMARY THREAT BEING DAMAGING WINDS...LARGE HAIL AND TORNADOES. RAINFALL AMOUNTS FROM THE STORMS IS ALSO EXPECTED TO BE HEAVY AT TIMES. THAT WILL RESULT IN AN INCREASED RISK OF FLOODING... ESPECIALLY NEAR RIVERS AND STREAMS. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY ON MONDAY AFTERNOON...STRONG NORTHWEST WINDS OF 20 TO 30 MPH ARE FORECAST TO OVERSPREAD THE REGION. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EVENING. LMZ521-522-541>543-111700- THE BAY OF GREEN BAY SOUTH OF A LINE FROM CEDAR RIVER MI TO ROCK ISLAND PASSAGE-LAKE MICHIGAN FROM WASHINGTON ISLAND TO SHEBOYGAN- 1154 AM CDT SUN APR 10 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHWEST LAKE MICHIGAN AND THE WATERS OF GREEN BAY. .DAY ONE...THIS AFTERNOON AND TONIGHT MOIST AIR MOVING NORTH OVER THE COLD WATERS OF LAKE MICHIGAN WILL BRING AREAS OF DENSE FOG FROM TIME TO TIME. THUNDERSTORMS ARE ALSO EXPECTED LATE THIS AFTERNOON AND EVENING. SOME OF THESE STORMS MAY BE ABLE TO PRODUCE DAMAGING WINDS AND LARGE HAIL. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THE PROBABILITY FOR WIDESPREAD SEVERE WEATHER IS LOW. AK
The Green Bay radar (KGRB), 47 km away, was scanning. The volume nearest the first event began at 21:30 UTC.
19 hail, 15 tornado, 15 thunderstorm wind, 3 funnel cloud. Local standard time, as filed.
Thunderstorms produced penny size hail that covered the ground a couple miles southwest of the city of Kewaunee.
Thunderstorms produced golf ball size hail that fell in Kewaunee.
Thunderstorms produced penny size hail that fell at the intersection of 3rd Street and Ellis Street in Kewaunee.
Thunderstorms produced lime size hail that fell at Kewaunee.
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.
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.
Thunderstorms produced penny size hail that fell near New Rome.
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.
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.
Thunderstorms produced quarter size hail that fell near the intersection of County Road C and Interstate 39.
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.
Thunderstorms produced penny size hail that fell around Almond near Interstate Highway 39.
Thunderstorms produced golf ball size hail and a rotating wall cloud at Wild Rose.
Thunderstorm wind gusts of 80 to 90 mph downed 12-inch diameter trees in western Waushara County.
Thunderstorm wind gusts downed trees in Elcho.
Thunderstorms produced penny size hail that fell north of Wild Rose.
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.
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).
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).
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.
Thunderstorms produced half dollar size hail that fell north of Argonne.
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.
Thunderstorms produced penny size hail that fell west of Winchester.
Thunderstorms produced golf ball size hail that fell at Wautoma.
Thunderstorms produced golf ball size hail that fell at Argonne.
Thunderstorms produced 2 inch diameter hail near Crandon.
A ham radio operator spotted a funnel cloud near Dale in southwest Outagamie County.
Thunderstorm wind gusts to 80 mph downed large trees about 4 miles north of Wautoma.
Penny size hail fell east of Wild Rose and wind gusts reached 60 mph.
Thunderstorms produced gusts to 60 mph along with penny size hail.
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.
Golf ball size hail fell 2 miles east of Wild Rose.
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.
Quarter size hail fell at Pine River.
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.
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.
Baseball size hail fell north of Winneconne on County Highway M.
A funnel cloud was spotted on Oak Ridge Road in Winnebago County.
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.
Thunderstorms produced penny size hail that fell near the intersection of State Highways 15 and 76.
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.
Thunderstorms southeast of Appleton produced a measured wind gust of 60 mph.
Thunderstorm wind gusts to 75 mph downed trees southwest of Oshkosh.
Thunderstorm winds damaged a small building on Country Road D.
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.
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 gusts of 50 to 60 mph downed power lines in Brillion.
A school in Chilton measured a thunderstorm wind gust of 64 mph.
Thunderstorm winds downed trees in Reedsville.
A funnel cloud was spotted at Cooperstown Road near Denmark, in eastern Brown County.
Thunderstorms in Manitowoc produced estimated wind gusts to 65 mph.
Thunderstorm winds downed trees in Cleveland.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wisconsin in 2011Every state in 2011This day in weather historyThe tornado archive for Wisconsin, 2011Warnings in Wisconsin, April 2011
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 297496, 297497, 297495, 297494, 285243, 285246, 297493, 285259, 286808, 301542, 285283, 297491, 297490, 300842, 300866, 297489, 300856, 286812, 286831, 285272, 297498, 286836, 297488, 297484, 297486, 297487, 301117, 300858, 297483, 301150, 285275, 297481, 285305, 297480, 285282, 285306, 297479, 301131, 300885, 301548, and more.