EF1 tornado, Wyattville to Trempealeau, Minnesota, December 15, 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 mphthis tornado

   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 mph

   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

EF1

Date

December 15, 2021

Touchdown

8:17 PM CST (02:17 UTC)

Lifted

8:21 PM CST (02:21 UTC)

On the ground

4 minutes

Path length

4.8 miles (7.8 km)

Path width

40 yards (37 m)

Deaths

0

Injuries

0

Property damage

$125,000

Counties

Winona and Trempealeau counties

Touchdown point

43.996, -91.580

Lift-off point

44.054, -91.525

Record number

2112152017-01

71 damage points were recorded along this path by NWS ARX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 107 mph.

• Some softwood tree limbs down as well. Broad.
• Siding thrown into field to the north
• Buildings look ok. Good swath of downed trees. Mostly cleaned up
• Odd pattern. Maybe a microburst.

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

An intense storm system moved across the Upper Midwest on December 15th and produced a rare severe weather outbreak across southeast Minnesota. One person was killed near Rochester (Olmsted County) when a large tree fell on the victim. Twelve tornadoes occurred across parts of Mower, Fillmore, Houston, Dodge, Winona and Wabasha Counties. Eight of these tornadoes were rated EF1 with the others rated EF0. The tornadoes largely moved through rural areas damaging trees, power lines and farm buildings with the exception of an EF0 tornado that moved through the eastern sections of Preston (Fillmore County) and and EF1 tornado that tracked across Homer (Winona County). In addition to the tornadoes, damaging winds occurred with several reports of wind speeds over 70 mph. The highest recorded wind gusts were 85 mph in Plainview (Wabasha County), 84 mph in Harmony (Fillmore County) and Mabel (Fillmore County) and 83 mph south of Grand Meadow (Mower County). A state of emergency was declared in Fillmore County. The Governor of Minnesota authorized emergency assistance for the following counties: Dodge, Fillmore, Houston, Mower, Olmsted and Wabasha.

An intense storm system moved across the Upper Midwest on December 15th and produced a rare severe weather outbreak across western Wisconsin. Eight tornadoes occurred across parts of Trempealeau, Jackson and Clark Counties. Four of these tornadoes were rated EF2 and three EF1. The most substantial damage from the EF2 tornadoes occurred in Clark County. One tornado destroyed a home in the southwest corner of the county near Five Mile Creek west of Neillsville (Clark County). Another tornado caused extensive damage to farms and trees after moving through Stanley (Chippewa County) into the northwest corner of Clark County. An EF0 tornado passed through Perrot State Park (Trempealeau County) and damaged several homes on the west edge of Trempealeau (Trempealeau County). The other tornadoes largely moved through rural areas damaging trees, power lines and farm buildings. Because of the severe weather threat, the Rotary Lights display in La Crosse (La Crosse County) was closed for the first time in over 26 years where two temporary structures were destroyed.

This short-lived EF0 tornado moved over rural areas southeast of Lewiston. Farm outbuildings, a garage and trees were damaged by the tornado.

An EF1 tornado formed on a ridge top southwest of Homer, moved northeast across Homer before moving out over the Mississippi River and into Trempealeau County, Wisconsin. The main damage occurred on the ridge top to trees and outbuildings. By the time the tornado reached Homer, it was weakening and damage was mainly limited to trees.

This EF1 tornado initially formed in Winona County Minnesota before crossing the Mississippi River and moving through the Trempealeau Wildlife Refuge. Hundreds of trees were damaged by the tornado before it dissipated along the northeast side of the refuge.

This short-lived EF0 tornado likely formed over the Mississippi River, moved inland and across a portion of Perrot State Park before dissipating on the very western edge of Trempealeau. Extensive tree damage occurred in the state park and several homes were damaged when trees fell on them.

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

19 minutes of warning. NWS ARX issued a tornado warning for this county at 01:58 UTC, 19 minutes before the tornado touched down, in force until 02:29 UTC.

The county was under a tornado watch, issued at 23:30 UTC and running to 03:17 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 Moderate Risk, with a 0.10 chance of a tornado within 25 miles. The outlook in force was issued at 00:54 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.

Winona Municipal (ONA), 14 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), 37 km away, was scanning. The volume nearest the touchdown began at 02:18 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 MinnesotaEvery tornado in Minnesota since 1950Warnings in force in Minnesota nowThe forecast where you are

124 more were confirmed in the United States that day.

All 125 of them

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.