EF3 Boscobel tornado, Wisconsin, August 7, 2021

1. EF065 to 85 mph

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. EF186 to 110 mph

   Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

3. EF2111 to 135 mph

   Considerable damage. Roofs torn off well-built houses, frame homes shifted on their foundations, mobile homes destroyed, large trees snapped or uprooted, cars lifted off the ground.

4. EF3136 to 165 mphthis tornado

   Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

5. EF4166 to 200 mph

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. EF5over 200 mph

   Incredible damage. Strong frame houses swept off their foundations, car-sized missiles thrown more than 100 meters, steel-reinforced concrete badly damaged, high-rise buildings deformed.

7. Unrated

   The survey recorded a tornado but could not put a number on it, most often because it crossed open country and damaged nothing a rating can be read from.

Rating

EF3

Date

August 7, 2021

Touchdown

4:29 PM CDT (21:29 UTC)

Lifted

4:56 PM CDT (21:56 UTC)

On the ground

27 minutes

Path length

9.4 miles (15.1 km)

Path width

1,100 yards (1006 m)

Deaths

0

Injuries

0

Property damage

$430,000

Crop damage

$25,000

County

Grant County

Touchdown point

43.130, -90.720

Lift-off point

43.076, -90.549

Record number

2108071529-01

90 damage points were recorded along this path by NWS ARX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF3. The highest wind the damage implies is 160 mph.

• Tree branches snapped. Roof decking ruffled.
• Poles look old. More EF0 ish
• Inflow in the immediate north side of track
• Inflow on north side of track

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

Several rounds of storms moved across western Wisconsin during the afternoon of August 7th. One of these storms produced an EF3 tornado that started in Boscobel (Grant County) and traveled east/southeast before dissipating south of Blue River (Grant County). Along the path of the tornado, 6 homes sustained enough damage to be considered total losses but no injuries occurred. Flash flooding caused a mud slide along State Highway 33 southeast of La Crosse (La Crosse County) and washed out part of County Road NN south of St. Joseph (La Crosse County). Water also covered portions of State Highway 27 and County Roads J and X near Melvina (Monroe County). Coon Creek went out of its banks and caused extensive damage to the baseball field in Coon Valley (Vernon County). A county wide disaster was declared by Vernon County officials because of the flood damage.

A NWS storm survey confirmed that an EF3 tornado occurred across northern Grant County. The tornado started in Boscobel where damage to trees, power poles and power lines occurred. The tornado then moved east/southeast before dissipating south of Blue River. Along the path, six homes sustained enough damage to be considered total losses while numerous other had minor to moderate damage. No injuries were reported.

From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.

10 minutes of warning. NWS ARX issued a tornado warning for this county at 21:19 UTC, 10 minutes before the tornado touched down, in force until 22:00 UTC.

Every warning and watch covering the touchdown point that day, from the Iowa Environmental Mesonet's archive of National Weather Service products. Lead time is measured from the issue of the warning in force to the touchdown time in the database, both of which were recorded to the minute by different people.

The Storm Prediction Center had this point in a Slight Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 19:55 UTC.

SPC's Day 1 convective outlook as it stood when the tornado began, read at the touchdown point. The same archive is on the radar archive.

The radiosonde launches on either side of the tornado, from the nearest station that was launching then, drawn and analyzed the way Storm Lab does: the same diagram, the same parcel and shear definitions SPC's mesoanalysis uses.

Boscobel (OVS), 7 km from the path, in the two hours either side.

From the Iowa Environmental Mesonet's archive of airport observations.

The La Crosse radar (KARX), 92 km away, was scanning. The volume nearest the touchdown began at 21:29 UTC.

Open the radar archive at this moment, over the track

Reflectivity and velocity, decoded from the Level II archive in the browser. Volumes take a few seconds to open the first time.

Local storm reports within 60 km of the path, in the three hours either side.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

The live radar over the trackEvery 2021 tornado in WisconsinEvery tornado in Wisconsin since 1950Warnings in force in Wisconsin nowThe forecast where you are

2 more were confirmed in the United States that day.

Ratings are the survey's, read off the damage rather than measured; the rating scale is above. Tornado counts rise through the record as reporting improved, so a year in the 1950s is not comparable with one today except for the strongest tornadoes, which were always noticed.

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.