A brief tornado touched down near Fennimore (Grant County) in the early afternoon of May 9th as scattered thunderstorms moved across the area. The tornado was only on the ground for a couple of minutes but damaged a machine shed, barn, trees and blew windows out of a house.
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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 brief tornado touched down near Fennimore (Grant County) in the early afternoon of May 9th as scattered thunderstorms moved across the area. The tornado was only on the ground for a couple of minutes but damaged a machine shed, barn, trees and blew windows out of a house. Thunderstorms also moved across the region in the morning with lightning striking a school in Fennimore (Grant County). A small fire resulted on the roof of the building and school was delayed for two hours.
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 May 9, 2:36 AM CST, 2 hours 39 minutes earlier.
Area Forecast Discussion National Weather Service La Crosse WI 336 AM CDT Wed May 9 2018 .SHORT TERM...(Today through Thursday Night) Issued at 336 AM CDT Wed May 9 2018 GOES-East showing a fairly strong pv-anomaly rotating northeast through southwest MN with associated surface low moving through northern IA. Pv-advection along with warm air/moisture advection was producing an fairly expansive area of showers and scattered thunderstorms across our forecast area. Meanwhile, temperatures as of 3 am were in the 50s. Heaviest rainfall has been across portions of northeast IA were radar was indicating anywhere from 1/4 to as much as 1.75 has fallen. For today, will be watching that mid-level and surface wave continue rotating east across the area. This will continue showers and embedded thunderstorms to continue this morning, lessening in coverage from west to east as the day wears on as the wave begins to pull east of the area by early this evening. A few lingering shower will continue into this evening east of the Mississippi River, exiting after midnight. Otherwise, plan on clouds scattering from west to east with lows dropping into the middle 40s to the lower 50s. Thursday will see a mix of sun and clouds, with thickening clouds mainly west of the Mississippi River along wit a slight chance of showers. this will be in response to increasing isentropic lift and moisture transport ahead of low pressure and warm front lifting northeast out of the High and Central Plains. Easterly flow and increasing cloud cover will keep temperatures below normal with highs topping off in the upper 50s across north central WI to the lower 70s across far northeast IA/southwest WI. Showers and a few embedded thunderstorms will quickly overspread the area Thursday night as moisture transport and isentropic lift increases ahead of the aforementioned wave of low pressure lifting into eastern NE/western IA. .LONG TERM...(Friday through Tuesday) Issued at 336 AM CDT Wed May 9 2018 Showers and isolated thunderstorms continue through Friday as that wave of low pressure ripples across the area. With thick cloud cover/precipitation/chilly northeast flow, plan on a raw day with temperatures only making it into the 40s along/north of I-90 and 50s/lower 60s across northeast IA/far southwest WI. Rain chances continue into Saturday as yet another wave of low pressure ripple through the Plains toward the Ohio River Valley. Highest rain chances look to be along/south of I-90. Otherwise, another not-so-nice day as temperatures will only make it into the 50s. Aerial average rainfall from Thursday through saturday looks to be in the 1/2 to 1.5 inch range. However, embedded convection could produce localized heavier amounts. Will have to keep an eye out for water issues. See Hydrology sections below. We catch a break a break from the rain Sunday as high pressure finally builds into the region. Look for highs in the 60s to lower 70s. Monday is shaping up to be a spectacular day with plenty of sun and highs in the 70s. Shower and thunderstorm chances move back in for Monday night into Tuesday in advance of a vigorous wave of low pressure lifting out of the Rockies into the Plains. remaining warm though with highs Tuesday slated to be in the upper 70s/near 80. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1142 PM CDT Tue May 8 2018 Regional radars are showing an expansion in the coverage of showers and storms over southern Minnesota and northern Iowa in response to the approaching short wave trough and the increased moisture transport into the area. The 09.03Z suggests around 500 J/kg of MU CAPE will be reach into the KRST area for a couple of hours early in the overnight and will go with a period of thunder. The nose of the CAPE axis will be close to KLSE and a tempo for thunder may need to be added there as well. This activity should push past both airports before sunrise with the ceilings going down to MVFR behind the rain. These ceilings are then expected to remain down for much of Wednesday as another short wave trough moves across the region. This wave could produce a few more showers but confidence on placement and timing not high enough to include at this time, but could end up being east of both airports. The ceilings should then improve to VFR Wednesday evening as a weak area of high pressure tries to build in over the area. && .HYDROLOGY... Issued at 336 AM CDT Wed May 9 2018 Minor flooding continues along the lower reaches of the Kickapoo River at Steuben (expected to fall below flood stage this morning, and Mississippi River at McGregor and Guttenberg. Plan on scattered showers and a few thunderstorms continuing today. In general, additional rainfall amounts around 1/4 to 1/2 inch are expected, though with any convective (thunderstorm) elements, locally heavier amounts are possible. At this time, the threat for additional flooding through today is low but will have to watch to make sure storms don't line up over the same areas for too long (looks pretty progressive). More rounds of rain are likely Thursday night into Saturday, with some potential for additional heavy rainfall of 1-2 inches/locally higher in some areas. Right now, the heaviest rain threat appears near the Interstate 90 corridor but will need to watch latest forecast trends to nail down the details. Should those amounts be realized, additional flooding will be possible. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && SHORT TERM...DAS LONG TERM...DAS AVIATION...04 HYDROLOGY...DAS/Lawrence
Hazardous Weather Outlook National Weather Service La Crosse WI 451 AM CDT Wed May 9 2018 IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029- 032>034-041>044-053>055-061-101000- 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- 451 AM CDT Wed May 9 2018 This Hazardous Weather Outlook is for portions of southeast Minnesota...northeast Iowa and southwest into central Wisconsin. .DAY ONE...Today and Tonight Isolated thunderstorms are expected today. The primary threats will be lightning and localized heavy downpours. Minor flooding will continue today and tonight along stretches of the Mississippi River mainly south of Genoa Wisconsin. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday Isolated to scattered thunderstorms are possible Thursday night through Friday night. The primary threats will be lightning and localized heavy downpours. Pockets of heavier rainfall may produce rises on area rivers and streams. Minor flooding will continue into early next week along stretches of the Mississippi River mainly south of Genoa Wisconsin. .SPOTTER INFORMATION STATEMENT... Any rainfall reports would be appreciated. .EMERGENCY MANAGEMENT COORDINATION... No webinar is scheduled. DAS
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
609 AM CDT WED MAY 9 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0549 AM HEAVY RAIN DECORAH 43.30N 91.79W
05/09/2018 M2.44 INCH WINNESHIEK IA MESONET
MESONET STATION DECRH, DECORAH.
0549 AM HEAVY RAIN MCGREGOR 43.02N 91.19W
05/09/2018 M2.16 INCH CLAYTON IA MESONET
MESONET STATION MGRGR, MCGREGOR.
&&The national radar mosaic for the moment the first event began.
1 lightning, 1 tornado. Local standard time, as filed.
A lightning strike started a small fire on the roof of the Fennimore elementary school. The fire was extinguished before it reached the interior of the school. The start of school was delayed for two hours.
An EF-0 tornado touched down outside of Fennimore along Golf Road. The tornado was on the ground for approximately two minutes and damaged a machine shed, barn, trees and blew windows out of a house.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wisconsin in 2018Every state in 2018This day in weather historyThe tornado archive for Wisconsin, 2018Warnings in Wisconsin, May 2018
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: 757610, 752504.