Tornadoes · United States · Wisconsin · 2024
EF1 tornado, Longwood to Poniatowski, Wisconsin, May 21, 2024
From Longwood to Poniatowski, this EF1 tornado ran 4.0 miles across Clark and Marathon counties on May 21, 2024, touching down at 7:34 PM CDT and reaching 110 yards wide. It killed nobody, and did $345,000 of property damage.
The rating scale
Tracks are drawn in the color of the rating. The Enhanced Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.
EF065 to 85 mph
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
EF186 to 110 mphthis tornado
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
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.
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.
EF4166 to 200 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
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.
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.
The record
- Rating
- EF1
- Date
- May 21, 2024
- Touchdown
- 7:34 PM CDT (00:34 UTC)
- Lifted
- 7:37 PM CDT (00:37 UTC)
- On the ground
- 3 minutes
- Path length
- 4.0 miles (6.5 km)
- Path width
- 110 yards (101 m)
- Deaths
- 0
- Injuries
- 0
- Property damage
- $345,000
- Crop damage
- $14,000
- Counties
- Clark and Marathon counties
- Touchdown point
- 44.841, -90.325
- Lift-off point
- 44.888, -90.300
- Record number
- 2405211834-01
The damage survey
79 damage points were recorded along this path by NWS ARX and NWS GRB, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 107 mph.
- Barn not anchored or fastened
- Narrow but strong damage swath in satellite data.
- Major loss of roofing on barn
- Report from EM. Damage cleaned up prior to survey.
Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.
What the Weather Service recorded
On May 21st, a line of severe storms moved through the region during the late afternoon and evening hours bringing widespread wind damage and several tornadoes across western Wisconsin. Additionally, a few storms produced large hail across portions of southwestern Wisconsin.
A line of thunderstorms developed ahead of a cold front during the early evening on Tuesday (5/21) and tracked through much of northeast Wisconsin through the rest of the evening. Straight line winds produced wind damage along with 5 tornadoes.
This tornado occurred on the left flank of a broad area of downburst wind damage with the tornado path intermittent in nature as the downburst mixed in at times. Multiple farmsteads were hit with damage mainly to trees and outbuildings.
This was a brief tornado that damaged a farmstead and trees.
This was a weak and brief tornado that damaged a farmstead and a grove of trees.
A tornado developed just southwest of the Village of Unity in Clark County (NWS La Crosse warning area) at 7:34 pm CDT. The tornado produced damage in the western portion of Unity before crossing Highway 13 into western Marathon County at 7:35 pm CDT while producing additional damage in the northeast side of Unity including damage to an outbuilding along County Highway P. The tornado continued to produce scattered tree damage as it tracked northeast across Chokecherry Road and Juneberry Road. The tornado lifted near Mulberry Road at 7:41 pm CDT with straight line winds continuing northeast to County Road N just southeast of Colby. Total path length is estimated to be 4.07 miles long, with a width of 110 yards. Peak wind estimated to be around 105 mph.
A tornado touched down southwest of Unity, moved through the village, and ended northeast of town in Marathon County (NWS Green Bay's warning area). Besides damage to trees and power lines, several homes and garages had extensive damage, especially to roofs.
A tornado formed at 7:47 pm CDT west of Fenwood in western Marathon County and continued northeast before dissipating at 7:50 pm CDT. Total path length is estimated to be 2.11 miles long, with a width of 60 yards. Peak wind estimated to be around 87 mph.
A tornado formed at 7:51 pm CDT northwest of Edgar in western Marathon County and continued northeast before dissipating at 7:54 pm CDT between the village of Athens and the town of Rib Falls. Total path length is estimated to be 2.13 miles long, with a width of 80 yards. Peak wind estimated to be around 92 mph.
From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.
What forecasters said that day
The local office's own words before the tornado touched down, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS La Crosse, WI wrote its last area forecast discussion before the tornado touched down at May 21, 6:45 PM CDT, 49 minutes earlier. Its key messages:
- Significant severe weather event with a MODERATE RISK (Threat level 4 of 5) for severe storms late this afternoon/evening. Another rounds of storms expected late this afternoon into evening. The highest severe threat appears to begin late afternoon and into the evening with damaging wind gusts and tornadoes being the primary threats, large hail is a secondary threat.
- With additional 1 to 2 inches of QPF through tonight. This could cause rises on area rivers and streams. With increase rainfall rates in the stronger showers/storms, ponding of water on roadways can be expected.
- Shower/storm chances increase for Thursday night into Friday. Severe potential is still to early to discern due to timing of front.
Area forecast discussion, May 21, 6:45 PM CDT, 49 minutes before
Area Forecast Discussion
National Weather Service La Crosse WI
645 PM CDT Tue May 21 2024
.KEY MESSAGES...
- Significant severe weather event with a MODERATE RISK (Threat
level 4 of 5) for severe storms late this afternoon/evening.
Another rounds of storms expected late this afternoon into
evening. The highest severe threat appears to begin late
afternoon and into the evening with damaging wind gusts and
tornadoes being the primary threats, large hail is a secondary
threat.
- With additional 1 to 2 inches of QPF through tonight. This
could cause rises on area rivers and streams. With increase
rainfall rates in the stronger showers/storms, ponding of
water on roadways can be expected.
- Shower/storm chances increase for Thursday night into Friday.
Severe potential is still to early to discern due to timing of
front.
&&
.MESOSCALE...
Issued at 235 PM CDT Tue May 21 2024
At 19Z, surface analysis showed the main low pressure center
undergoing cyclogenesis in southwestern IA with 5mb/3hr
pressure falls over nwrn WI. A maritime tropical airmass warm
front was located roughly along I-80 with gusting southerly
winds to 25-30kt. Secondary frontal boundary extends as an
inverted trough from the low to about Duluth...another area of
convergence and destabilization occurring south of it.
Mainly monitoring the return flow and destabilization over the
next hours as the wind field is in place. KDMX wind profile has
70+ 0-6km bulk shear, and 37 kts in the 0-1km layer with a
potent 300 m2/s2 of 0-500m SRH. A very serious wind profile for
supercell tornadoes, and severe weather in general.
Using WoFS guidance over the area, values of 5+ surge northward
to about I-94 (remarkably!) but just south of the Twin Cities
by 6 pm, so some serious destabilization with big dynamical lift
coming in. There seems to be a slight preference for southeast
MN into northcentral WI for a higher probability footprint for
0-2km vertical vorticity swaths over nc IA into sern MN, with
more sporadic signals further south, meaning there may be a
slight preference for that area through 6 pm for tornadoes.
Current forecast is on track, with generally a 5pm to 9 pm
window from I-35 to I-39 in WI.
Also, there is signal that an initial line will move in to the
western areas just east of I-35, but storms will develop out
ahead and possibly a discrete phase of storms along the Miss
river in concert. This is verified in the HRRR and WOFS runs
over the past many hours. So, be careful with assuming steady
state motion of the initial storms and no downstream
development.
&&
.DISCUSSION...
Issued at 336 PM CDT Tue May 21 2024
This Evening into Thursday
Latest water vapor satellite imagery indicates vigorous shortwave
trough over eastern Nebraska and producing showers/storms across
western Iowa/southern Minnesota. This shortwave trough will
lift northeastward over the forecast area late this afternoon
and evening and spread showers/storms into the forecast area.
Severe potential with the storms is expected with these storms
especially this evening and the details of the parameters are in
the above Mesoscale section. Main severe threat are damaging
winds and tornadoes.
With the recent 1 to 3 inches of rain falling over the southern
half of the forecast area...along with the potential of another
inch this afternoon/evening. This will cause rises on area
rivers and ponding of area roadways. In addition...precipitable
water values of around 1.50 inches and decent moisture
transport/deformation band setting up over the northern half of
the forecast area...rainfall amounts of 1 to 2 inches is
expected this evening/tonight...especially over north central
Wisconsin.
Cold front associated with shortwave trough moves east of the area
tonight. Subsidence behind cold front and tight pressure gradient
will allow for wind speeds to be 20 to 25 knots with gusts 30 to 35
knots across much of the forecast area.
Cooler airmass advects into the forecast area Wednesday. Much of the
forecast area will remain dry. However...north central Wisconsin
will continue to be under the influence of the shortwave trough.
With daytime heating...bufkit soundings showing instability and
breaking the cap over this area...scattered showers and few storms
will develop during the afternoon hours. These showers/storms will
diminish near sunset. Then...weak surface ridge builds into the
Upper Mississippi River Valley Thursday and area should remain dry
for much of the day.
Focus turns to Thursday night into Friday. Another shortwave trough
moves across the Northern Plains/Upper Great Lakes Region. There is
decent moisture convergence/vertical motion with the shortwave
trough. Showers/storms are expected and will move across the
forecast area west to east during the day Friday. Timing of
showers/storms continue to be an issue with the deterministic
GFS/NAM/ECMWF. Severe threat with the storms is still too early to
discern...based on timing of surface features/showers/storms.
Main forecast concerns from Friday night through
Tuesday are shower/storm chances through the forecast period. Flow
pattern aloft becomes west to east zonal flow across the Upper Great
Lakes Region early in the forecast period Saturday into Sunday.
Then...upper level trough develops over the Upper Great Lakes Region
late in the forecast period. Weak pieces of energy embedded in the
west to east flow aloft may produce some showers/storms Saturday
into Sunday...however these are low chances less than 40 percent.
With upper level trough digging over the Upper Great Lakes Region
shortwave troughs are expected to track over the Upper Mississippi
River Memorial Day into Tuesday. The main issue Memorial Day into
Tuesday is the placement/track of the shortwave troughs associated
with the upper level trough. This will impact where convection
develops over the forecast area and will continue chances of
scattered showers/storms for both days. High temperatures Saturday
into Tuesday are expected to be near to slightly below normal with
highs into the middle 60s to middle 70s.
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 644 PM CDT Tue May 21 2024
A line of strong to severe storms is approaching KLSE. It will
affect this TAF site through 22.00z. Carried wind gusts up to 50
knots. Showers and storms will continue at KRST through 22.02z
and KLSE through 22.03z. In the wake of these storms, there will
be IFR/MVFR ceilings. These will last much of the night and then
become VFR between 22.13z and 22.15z.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Flood Watch until 9 PM CDT this evening for MNZ079-086>088-
094>096.
IA...Flood Watch until 9 PM CDT this evening for IAZ008>011-018-019-
029-030.
&&
MESOSCALE...Baumgardt
DISCUSSION...DTJ
AVIATION...BoyneHazardous weather outlook, May 21, 2:59 PM CDT, 4 hours 35 minutes before
Hazardous Weather Outlook National Weather Service La Crosse WI 259 PM CDT Tue May 21 2024 IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029- 032>034-041>044-053>055-061-230000- Mitchell-Howard-Winneshiek-Allamakee-Floyd-Chickasaw-Fayette- Clayton-Wabasha-Dodge-Olmsted-Winona-Mower-Fillmore-Houston- Taylor-Clark-Buffalo-Trempealeau-Jackson-La Crosse-Monroe-Juneau- Adams-Vernon-Crawford-Richland-Grant- 259 PM CDT Tue May 21 2024 This Hazardous Weather Outlook is for portions of southeast Minnesota...northeast Iowa and southwest into central Wisconsin. .DAY ONE...This afternoon and Tonight Additional storms are expected through this evening with peak time for severe storms from 5 to 9 PM. Damaging wind gusts, some 75mph+, tornadoes, some strong, and locally heavy rain are the primary severe weather threats this afternoon and evening. Large hail will also be possible. Be alert to the potential for significant severe weather through this evening. Be extra weather aware and prepared to take action and move to a safe location/sturdy building away from trees. Due to the multiple rounds of thunderstorms, localized areas may receive several inches of rain. As a result, the threat for river rises and flooding will be on the increase. Those with interests along area creeks, streams, and rivers should monitor conditions. Be prepared to alter travel plans during heavy rains or severe weather. .DAYS TWO THROUGH SEVEN...Wednesday through Monday The next chance for thunderstorms will be Friday. It is too early to discern the severe weather threat at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation will likely be needed through this evening. .EMERGENCY MANAGEMENT COORDINATION... No webinar scheduled. NOFWD
In the hours before
Local storm report, May 21, 7:24 PM CDT, 10 minutes before
Preliminary Local Storm Report
National Weather Service La Crosse WI
724 PM CDT Tue May 21 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0703 PM Tstm Wnd Dmg Sparta 43.94N 90.81W
05/21/2024 Monroe WI Emergency Mngr
Trees and power lines down.
&&Local storm report, May 21, 7:25 PM CDT, 9 minutes before
Preliminary Local Storm Report
National Weather Service La Crosse WI
725 PM CDT Tue May 21 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0722 PM Tstm Wnd Gst Elkader 42.86N 91.40W
05/21/2024 E50 MPH Clayton IA Emergency Mngr
&&Local storm report, May 21, 7:26 PM CDT, 8 minutes before
Preliminary Local Storm Report
National Weather Service La Crosse WI
726 PM CDT Tue May 21 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0719 PM Tstm Wnd Gst Tomah 43.98N 90.50W
05/21/2024 E60 MPH Monroe WI Emergency Mngr
&&Local storm report, May 21, 7:27 PM CDT, 7 minutes before
Preliminary Local Storm Report
National Weather Service La Crosse WI
727 PM CDT Tue May 21 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0705 PM Tstm Wnd Dmg Hillsboro 43.65N 90.34W
05/21/2024 Vernon WI Emergency Mngr
Trees down on home.
&&Local storm report, May 21, 7:28 PM CDT, 6 minutes before
Preliminary Local Storm Report
National Weather Service La Crosse WI
728 PM CDT Tue May 21 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0642 PM Tstm Wnd Dmg 1 N La Crosse 43.84N 91.23W
05/21/2024 La Crosse WI Public
Large tree down over road in northside of La
Crosse.
&&Local storm report, May 21, 7:31 PM CDT, 3 minutes before
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</html>The air that afternoon
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.
Green Bay/Straub, WI (KGRB), 00:00Z
0.6 hours before the tornado, 180 km from the path. May 22, 2024.
- Mixed-layer CAPE
- 442 J/kg
- Mixed-layer CIN
- -98 J/kg
- Surface CAPE
- 232 J/kg
- Mixed-layer LCL
- 1016 m above ground
- 0-6 km bulk shear
- 57 kt
- 0-1 km bulk shear
- 11 kt
- 0-1 km storm-relative helicity
- 49 m²/s²
- 0-3 km storm-relative helicity
- 149 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.1
- 0-3 km lapse rate
- 5.5 K/km
Green Bay/Straub, WI (KGRB), 12:00Z
11.4 hours after it, 180 km from the path. May 22, 2024.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- -98567 J/kg
- Surface CAPE
- 404 J/kg
- Mixed-layer LCL
- 616 m above ground
- 0-6 km bulk shear
- 34 kt
- 0-1 km bulk shear
- 18 kt
- 0-1 km storm-relative helicity
- 106 m²/s²
- 0-3 km storm-relative helicity
- 86 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
- 0-3 km lapse rate
- 3.6 K/km
The surface observations
Medford (MDZ), 26 km from the path, in the two hours either side.
| Time (UTC) | Temp (°F) | Dew point (°F) | Wind | Gust (kt) | Pressure (mb) | Weather |
|---|---|---|---|---|---|---|
| 00:00 UTC |
From the Iowa Environmental Mesonet's archive of airport observations.
The radar
The La Crosse radar (KARX), 135 km away, was scanning. The volume nearest the touchdown began at 00:34 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.
This ground now
The live radar over the trackEvery 2024 tornado in WisconsinEvery tornado in Wisconsin since 1950Warnings in force in Wisconsin nowThe forecast where you are
The other tornadoes of May 21, 2024
42 more were confirmed in the United States that day.
| Date | Time | Rating | Where | Path (mi) | Width (yd) | Deaths | Injuries | Damage |
|---|---|---|---|---|---|---|---|---|
| May 21 | 4:54 AM CDT | EF0 | Polk, NE | 4.1 | 75 | $1.0 million | ||
| May 21 | 5:14 AM CDT | EF0 | Colfax, NE | 0.5 | 50 | |||
| May 21 | 5:23 AM CDT | EF0 | Butler, NE | 0.6 | 50 | |||
| May 21 | 5:27 AM CDT | EF0 | Butler, NE | 2.6 | 50 | |||
| May 21 | 5:45 AM CDT | EF0 | Saunders, NE | 0.4 | 50 | |||
| May 21 | 7:10 AM CDT | EF0 | Montgomery, IA | 0.7 | 40 | |||
| May 21 | 7:32 AM CDT | EF1 | Page, IA | 3.3 | 80 | |||
| May 21 | 12:52 PM CDT | EF0 | Saunders, NE | 0.2 | 50 | |||
| May 21 | 2:30 PM CDT | EF1 | Buena Vista, IA | 1.6 | 75 | |||
| May 21 | 2:35 PM CDT | EF1 | Montgomery, IA | 2.9 | 70 | |||
| May 21 | 2:43 PM CDT | EF3 | Page, IA | 33.9 | 1,300 | $1.0 million | ||
| May 21 | 2:57 PM CDT | EF1 | Page, IA | 1.7 | 85 | |||
| May 21 | 2:59 PM CDT | EF4 | Greenfield tornado, IA | 40.6 | 1,600 | 5 | 35 | $32 million |
| May 21 | 3:09 PM CDT | EF0 | Audubon, IA | 7.2 | 100 | $10,000 | ||
| May 21 | 3:18 PM CDT | EF1 | Adams, IA | 12.7 | 200 | $101,000 | ||
| May 21 | 3:39 PM CDT | EF2 | Adair, IA | 14.6 | 200 | $750,000 | ||
| May 21 | 3:48 PM CDT | EF0 | Martin, MN | 2.3 | 75 | |||
| May 21 | 3:50 PM CDT | EF0 | Union, IA | 4.0 | 75 | $20,000 | ||
| May 21 | 4:25 PM CDT | EF0 | Warren, IA | 1.0 | 40 | $30,000 | ||
| May 21 | 4:28 PM CDT | EF0 | Warren, IA | 2.0 | 75 | $10,000 | ||
| May 21 | 4:30 PM CDT | EF2 | Polk, IA | 40.8 | 1,000 | 4 | $8.4 million | |
| May 21 | 5:25 PM CDT | EF0 | Henry, MO | 0.3 | 50 | |||
| May 21 | 5:27 PM CDT | EF1 | Rogers, OK | 5.3 | 500 | $100,000 | ||
| May 21 | 5:39 PM CDT | EF1 | Rogers, OK | 1.0 | 100 | $10,000 | ||
| May 21 | 5:41 PM CDT | EF0 | Goodhue, MN | 0.7 | 25 | |||
| May 21 | 6:01 PM CDT | EF1 | Winona, MN to WI | 19.7 | 110 | $320,000 | ||
| May 21 | 6:14 PM CDT | EF1 | Buffalo, WI | 3.9 | 100 | $80,000 | ||
| May 21 | 6:17 PM CDT | EF1 | Buffalo, WI | 2.7 | 45 | $126,000 | ||
| May 21 | 6:34 PM CDT | EF1 | Trempealeau, WI | 0.8 | 150 | $79,000 | ||
| May 21 | 6:56 PM CDT | EF1 | Eau Claire, WI | 9.5 | 440 | |||
| May 21 | 6:59 PM CDT | EF1 | Jackson, WI | 3.1 | 75 | |||
| May 21 | 7:08 PM CDT | EF1 | Clark, WI | 7.0 | 300 | $140,000 | ||
| May 21 | 7:20 PM CDT | EF1 | Clark, WI | 9.1 | 120 | $88,000 | ||
| May 21 | 7:27 PM CDT | EF1 | Clark, WI | 4.0 | 150 | $270,000 | ||
| May 21 | 7:29 PM CDT | EF1 | Clark, WI | 2.2 | 75 | $70,000 | ||
| May 21 | 7:33 PM CDT | EF0 | Clark, WI | 1.4 | 75 | $33,000 | ||
| May 21 | 7:47 PM CDT | EF1 | Marathon, WI | 2.1 | 60 | |||
| May 21 | 7:49 PM CDT | EF1 | Dane, WI | 4.6 | 75 | $1.1 million | ||
| May 21 | 7:51 PM CDT | EF1 | Marathon, WI | 2.1 | 80 | |||
| May 21 | 7:59 PM CDT | EF1 | Marquette, WI | 5.3 | 60 | $60,000 | ||
| May 21 | 8:58 PM CDT | EF1 | Outagamie, WI | 2.7 | 80 | |||
| May 21 | 10:32 PM CDT | EF1 | Door, WI | 2.3 | 50 |
What this means
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.
Sources
NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.