A line of storms rolled across northeast Iowa during the afternoon of August 24th. These storms produced winds strong enough to cause wind damage from Floyd County east across Chickasaw County into Fayette County.
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 ARX wrote it up.
A line of storms rolled across northeast Iowa during the afternoon of August 24th. These storms produced winds strong enough to cause wind damage from Floyd County east across Chickasaw County into Fayette County. Trees were downed along U.S. Highway 63 near New Hampton (Chickasaw County) and 60 mph wind gusts in Oelwein (Fayette County) snapped and uprooted numerous trees and caused a building to partially collapse. One person was injured in Oelwein when they became trapped under the branches of a fallen tree. The Governor of Iowa issued a proclamation of disaster emergency for Fayette 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 La Crosse, WI wrote its last area forecast discussion before the first event at Aug 24, 11:17 AM CST, 1 hour 23 minutes earlier.
Area Forecast Discussion National Weather Service La Crosse WI 1217 PM CDT Tue Aug 24 2021 .SHORT TERM...(Today through Wednesday) Issued at 315 AM CDT Tue Aug 24 2021 MCS churning east across the Dakotas early this morning, working along the instability gradient in conjunction with the low level jet. HRRR doing a pretty good job with it currently, and the expectation is this will hold together, continue to run the instability/moisture transport gradient. This drives across north- central WI roughly between 15-18z, mostly along/north of I-94. Depending on how far south the storms build, they could tap into a hefty amount of instability. While likely still elevated in nature, effective shear of 30 to 40 kts would be possible (via the RAP). Strong to a few severe storms possible, with hail and wind the threats. Some hints that the cluster could become more linear, promoting bowing segments that regardless of near sfc stability, would result in an increased threat for strong (potentially damaging) winds. Going to have to watch this carefully. Severe Thunderstorm Watch is in effect just to the west across central MN. In addition, convection going up east of the MCS, on the edge of the instability/moisture transport and around the sfc front. Some are quickly upscaling with some threat for hail. Likely be some interaction with the MCS as the morning wears on. Meanwhile, same HRRR run pointing to expanding convection southwest, along cold front/outflow boundary with interaction from bits of upper level energy. Some support from the HOPWRF here. A more recent trend in the meso models, but one that has some support from likely forcing. Will need the sfc lift to get things going with low level capping in place. Confidence shaky in this outcome but will cover chances with low end pops. If it does get going, could quickly become strong/severe in this favorable environment. Anticipate updates to rain chances and any severe potential through day as current convection will have a bearing on how the rest of the day evolves. For tonight, with front expect to sag south/southeast across the forecast area, storm focus could/would shift to Iowa/southern WI. Farther north, pcpn chances will continue, mostly thanks to upper level energy and some help from moisture transport. Looking for a dry day? Wednesday still looking like the one for you. Can't rule out some small chances - mostly south - but the bulk of the area should get a break from storm chances. .LONG TERM...(Thursday through Monday) Issued at 315 AM CDT Tue Aug 24 2021 Challenging forecast when it comes to pcpn chances through the weekend. Various forcing mechanisms, synoptic and meso, along with a moist/warm airmass to fuel them. Where these lie/set up is uncertain with near term environment being adjusted by convection, sun vs cloud regions, etc. Trying to provide too much detail is problematic. Confidence is high that there will be showers/storms across the region from Thu-Sun, but where the higher chances will lie is not "set in stone". Will paint with a broad brush as a result, hoping to add more detail as we move through the week. KEY FORECAST POINTS: find the surface boundary, locate the low level jet (strength/moisture transport) and where it impinges on the boundary, ferret out if shortwave energy will enhance the low level lift. This region will be the most likely for shower/storms. Low level warming will serve to cap atmosphere south of the sfc front. Warm air advection, sloping frontogenetic forcing to aid north of boundary. MOISTURE/RAINFALL: yup, no problem here. Steady push of warm/moist air northward into the region with PWs mostly around 2 inches and warm cloud depths around 4500 m at times. Efficient rainmakers with locally heavy rain likely. With potential for training/repeated rounds of storms (west-east boundary) flooding could become a concern - especially if Friday's rain repeats over where Thursday's fall. Rainfall +5 inches through the period certainly possible for a few location. INSTABILITY/SHEAR: as you'd expect, the bulk of the instability resides in the warm sector (south of the front) in a mostly capped off environment. However, both the GFS and NAM suggest around 1000 J/kg of MUCAPE will be available for storm development. Good deep layer shear indicated in the models, but much of that in the 0-1km layer. With most storms expected to be elevated, they won't feel that. Still, effective shear could be decent, providing some aid to storm organization/updrafts. Of course, there is also the warm front itself, a source for sfc vorticity. Any storm that roots itself to that could spin. A few strong/isolated severe certainly possible over the period. Too many questions to give thumbs up/down to timing and where those would lie at this time. NEAR TERM ENVIRONMENT: the "best laid plans" (aka, the forecast) could go awry based on convective boundaries, sun/cloud temp influenced differentials, etc. Even the weakest of waves could spark storms that could change the course of convective potential for the rest the day. Meso analysis will be key for forecast adjustments. Anticipate changes to the forecast based on that. SENSIBLE OUTCOMES: overall trends in the GFS/EC suggest the bulk of the rain will fall across the northern half of the forecast area Thu/Thu night (southeast MN into central WI and north). This continues to be favored on Fri, although elongated vort energy stretching southwest could provide further focus that would impact southern parts of the area with higher rain chances. Sat could see a decent break from pcpn chances during the day, with more showers/storms returning later that night and Sun via an upper level shortwave trough. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 1217 PM CDT Tue Aug 24 2021 Local and regional radars show a line of convection progressing steadily east that should move across both airports early this afternoon. Will show MVFR conditions with this line. After that, much more uncertain on how much additional convection may form and where. The forcing for additional development looks to be very weak and the nearly stationary front in the Interstate 90 corridor should gradually sink south, so for now, will just carry a VCTS into the late afternoon before going dry with VFR conditions. With plenty of weak short wave troughs in the flow aloft, the potential exists that some additional convection could fire up, just unknown where and when at this point. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && SHORT TERM...Rieck LONG TERM....Rieck AVIATION...04
Hazardous Weather Outlook National Weather Service La Crosse WI 359 AM CDT Tue Aug 24 2021 IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029- 032>034-041>044-053>055-061-251000- 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- 359 AM CDT Tue Aug 24 2021 This Hazardous Weather Outlook is for portions of southeast Minnesota...northeast Iowa and southwest into central Wisconsin. .DAY ONE...Today and Tonight Scattered storms, mainly today. Some will be strong, potentially severe. Threats include hail, strong to damaging wind gusts, and locally heavy rain. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Storm chances through the weekend. A few will be strong, with isolated severe possible. Which days could hold a greater severe threat is uncertain. All storms will be capable of locally heavy rain with several inches of accumulation possible through Sunday. .SPOTTER INFORMATION STATEMENT... No action needed. .EMERGENCY MANAGEMENT COORDINATION... No webinar is scheduled. Rieck
Special Weather Statement
National Weather Service La Crosse WI
907 AM CDT Tue Aug 24 2021
WIZ017-029-241500-
Taylor WI-Clark WI-
907 AM CDT Tue Aug 24 2021
...Strong thunderstorms will impact portions of Clark and Taylor
Counties through 1000 AM CDT...
At 907 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 6 miles northwest of Sheldon to near Augusta.
Movement was east at 40 mph.
HAZARD...Winds in excess of 30 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
Medford, Colby, Thorp, Loyal, Greenwood, Owen, Rib Lake, Chelsea,
Westboro, Jump River, Longwood, Reseburg, Stetsonville, Goodrich,
Willard, Withee, Gilman, Curtiss, Lublin and Highway 73 And 98.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4512 9004 4512 9020 4503 9020 4503 9031
4461 9032 4459 9092 4538 9092 4538 9005
TIME...MOT...LOC 1407Z 257DEG 36KT 4539 9102 4463 9112
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...30 MPH
KurzPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
929 AM CDT TUE AUG 24 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0828 AM TSTM WND GST 2 N DORCHESTER 45.03N 90.33W
08/24/2021 M38 MPH CLARK WI PUBLIC
&&Special Weather Statement
National Weather Service La Crosse WI
1000 AM CDT Tue Aug 24 2021
WIZ044-241515-
Adams WI-
1000 AM CDT Tue Aug 24 2021
...A strong thunderstorm will impact portions of northeastern Adams
County through 1015 AM CDT...
At 959 AM CDT, Doppler radar was tracking a strong thunderstorm 9
miles northeast of Friendship, moving east at 25 mph.
HAZARD...Winds in excess of 40 mph and half inch hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
Locations impacted include...
Colburn, County Roads C And G, The Preston Cliffs, Highway 21 And
County G, County Roads G And O, The Ship Rock Wayside, The Colburn
Wildlife Area and County Roads O And W.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4397 8978 4416 8977 4420 8960 4398 8960
TIME...MOT...LOC 1459Z 256DEG 23KT 4406 8969
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH
KurzSpecial Weather Statement
National Weather Service La Crosse WI
1235 PM CDT Tue Aug 24 2021
IAZ008-018-MNZ094-241830-
Floyd IA-Mitchell IA-Mower MN-
1235 PM CDT Tue Aug 24 2021
...Strong thunderstorms will impact portions of Mitchell, northern
Floyd and Mower Counties through 130 PM CDT...
At 1234 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Geneva to near Mason City Municipal
Airport. Movement was east at 40 mph.
HAZARD...Winds in excess of 40 mph and pea size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
Locations impacted include...
Austin, Osage, Grand Meadow, St. Ansgar, Le Roy, Adams, Riceville,
Brownsdale, Lyle, Stacyville, Rose Creek, Lansing, Racine, Mayville,
Dexter, Mapleview, Waltham, Elkton, Mitchell and McIntire.
This includes Interstate 90 in Minnesota between mile markers 175 and
204.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4385 9305 4385 9269 4383 9269 4383 9245
4372 9245 4350 9249 4350 9255 4349 9255
4320 9256 4320 9302 4350 9303 4350 9305
TIME...MOT...LOC 1734Z 270DEG 33KT 4384 9318 4324 9338
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH
KurzSpecial Weather Statement
National Weather Service La Crosse WI
1238 PM CDT Tue Aug 24 2021
IAZ018-241845-
Floyd IA-
1238 PM CDT Tue Aug 24 2021
...Strong thunderstorms will impact portions of Floyd County through
145 PM CDT...
At 1237 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Mason City Municipal Airport to near
Belmond. Movement was east at 40 mph.
HAZARD...Wind gusts up to 50 mph and half inch hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
Locations impacted include...
Charles City, Rockford, Rudd, Floyd, Marble Rock, Colwell, Idlewilde
State Park, Roseville, Howardville, Oakwood, Powersville, Colwell
County Park, and Floyd Crossing.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.
&&
LAT...LON 4321 9302 4321 9256 4291 9267 4291 9303
TIME...MOT...LOC 1737Z 267DEG 35KT 4322 9337 4288 9359
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH
KurzSpecial Weather Statement
National Weather Service La Crosse WI
129 PM CDT Tue Aug 24 2021
IAZ008-009-MNZ094-095-241915-
Howard IA-Mitchell IA-Fillmore MN-Mower MN-
129 PM CDT Tue Aug 24 2021
...Strong thunderstorms will impact portions of eastern Mitchell,
Howard, southeastern Mower and southwestern Fillmore Counties through
215 PM CDT...
At 129 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Spring Valley to near Osage. Movement was
east at 40 mph.
HAZARD...Winds in excess of 30 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
Osage, Preston, Spring Valley, Le Roy, Riceville, Lanesboro, Elma,
Lime Springs, Wykoff, Fountain, Fillmore, Cherry Grove, Bristol,
York, Carimona, Ostrander, Chester, McIntire, Orchard and Whalan.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4376 9247 4376 9190 4321 9236 4321 9290
TIME...MOT...LOC 1829Z 266DEG 34KT 4371 9243 4321 9283
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...30 MPH
KurzThe La Crosse radar (KARX), 157 km away, was scanning. The volume nearest the first event began at 18:40 UTC.
5 thunderstorm wind. Local standard time, as filed.
Trees were blown over west of Charles City that also caused power lines to go down.
Trees were blown down along U.S. Highway 63 in Williamstown.
Trees were blown down southwest of Fredericksburg.
Parts of a roof were blown off a hog confinement building southwest of Oelwein.
An estimated 60 mph wind gust in Oelwein snapped or uprooted numerous trees. One person sustained injuries when they became trapped under the branches of a fallen tree. A building partially collapsed briefly trapping one person.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2021Every state in 2021This day in weather historyWarnings in Iowa, August 2021
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: 980551, 980552, 980553, 980558, 980554.