Throughout the evening hours on August 27th, a lone thunderstorm produced sporadic instances of hail up to quarter sized across portions of southeast Minnesota, primarily in Olmsted and Fillmore counties.
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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.
Throughout the evening hours on August 27th, a lone thunderstorm produced sporadic instances of hail up to quarter sized across portions of southeast Minnesota, primarily in Olmsted and Fillmore counties.
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 27, 5:46 PM CST, 47 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service La Crosse WI 646 PM CDT Wed Aug 27 2025 .KEY MESSAGES... - Showers and storms are expected this afternoon and evening primarily across southeast Minnesota, northeast Iowa, southwest Wisconsin (30-60%) and again overnight primarily across Wisconsin (30-50%). - Below normal temperatures are expected Thursday night into Friday morning, primarily across north-central Wisconsin. - Uncertainty surrounding the possibility of showers and storms this weekend. && .DISCUSSION... Issued at 152 PM CDT Wed Aug 27 2025 Showers and Storms this Afternoon and Overnight Across portions of southeast Minnesota, northeast Iowa, and into southwest Wisconsin, showers are expected to redevelop this afternoon into the overnight hours on the nose of 850hPa moisture transport and warm air advection coincident with forcing associated with a 500hPa shortwave trough pivoting through the Great Lakes region (30-60%). Some rumbles of thunder are possible with these showers during the afternoon hours given MLCAPE values increasing to 500-1000 J/kg associated with the moistening low levels, primarily over southeast Minnesota where the greatest instability should develop. Given weak effective shear of 25kts, not expecting organized storm development with lighting and heavy rain the primary threats. As the 500hPa shortwave trough pivots through the Upper Great Lakes region this evening into Thursday, a surface cold front will sink southward through Wisconsin, which will be the focus of additional shower and storm development overnight. Forcing associated with these features via 900-800hPa frontogenesis and QG ascent are strongest across northern and eastern Wisconsin. This suggests the highest probabilities for precipitation will reside largely to the north and east of our area. However, portions of north-central to central Wisconsin still have a 30-50% probability of precipitation as the front moves southward. Elevated instability should remain present overnight ahead of the front with MUCAPE values of 500-1000 J/kg noted in model soundings, which would promote some thunder and lightning. The strongest shear lies behind the front, so again not expecting any sort of organized convection. The front stalls across southern Wisconsin into northeast Iowa by Thursday afternoon. Weak convergence along this boundary appears to be the catalyst of additional shower development Thursday afternoon (10-15%), but where showers develop will be largely dependent on where the frontal boundary stalls. Below Normal Temperatures Thursday Night into Friday Morning Cold air advection behind the surface cold front moving southward tonight will bring unseasonably cool low temperatures back to the region Thursday night into Friday morning, specifically across Wisconsin. 70-80% of the members in the 27.00z EFI depict low temperatures below the model climatology indicative of these abnormal temperatures although the lack of a shift-of-tails suggests low temperatures are unlikely to be records. There is some uncertainty in how cold temperatures will get Thursday night dependent on how clear the skies are, but given the dry air behind the front, expecting skies to be mostly clear. As such, temperatures towards the 25th percentile of the model guidance seem reasonable. This results in low temperatures in the low 40s towards north- central Wisconsin and the low 50s towards northeast Iowa, generally 5-10 degrees below normal for those in Wisconsin. Shower and Storm Potential This Weekend Quite a bit of uncertainty regarding the evolution of the synoptic pattern and thus the surface conditions this weekend. 500hPa longwave ridging across the western United States slowly builds eastward Friday as a shortwave trough promotes low-level cyclogenesis over the Northern Plains. Where this cyclogenesis occurs though remains in question and will lead to the ultimate impacts we see across our area. The 27.00z GEFS suggests a much more eastward solution with lower heights developing over eastern South Dakota whereas the 27.00z EPS/GEPS develop the lower heights over western South Dakota. With the more eastward solution, probabilities of showers/storms across southeast Minnesota and northeast Iowa (currently 15-20%) will increase whereas the further westward solution will keep the higher probabilities across central and western Minnesota. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 639 PM CDT Wed Aug 27 2025 A band of scattered MVFR showers and storms over SE Minnesota and NE Iowa slowly shifts ESE and weakens prior to 06Z while a secondary band of MVFR showers grazes areas north of an EAU to ISW line during the same period. IFR to LIFR fog develops north of an AEL to PVB line after 08Z and lingers through the mid morning before lifting/scattering prior to 15Z. Light SSW winds tonight veer to the NE for the day on Thursday at 5-10 kts. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && DISCUSSION...Falkinham AVIATION...Skow
Hazardous Weather Outlook National Weather Service La Crosse WI 342 AM CDT Wed Aug 27 2025 IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029- 032>034-041>044-053>055-061-281100- 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- 342 AM CDT Wed Aug 27 2025 This Hazardous Weather Outlook is for portions of southeast Minnesota...northeast Iowa and southwest into central Wisconsin. .DAY ONE...Today and Tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... No action needed. .EMERGENCY MANAGEMENT COORDINATION... No webinar is scheduled. Boyne
Special Weather Statement
National Weather Service La Crosse WI
729 PM CDT Wed Aug 27 2025
MNZ087-094-095-280100-
Olmsted MN-Fillmore MN-Mower MN-
729 PM CDT Wed Aug 27 2025
...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN OLMSTED...
NORTHEASTERN MOWER AND NORTHWESTERN FILLMORE COUNTIES THROUGH 800 PM
CDT...
At 727 PM CDT, Doppler radar was tracking a strong thunderstorm 7
miles west of Stewartville, or 10 miles southwest of Rochester,
moving east at 25 mph.
HAZARD...Penny size hail.
SOURCE...Radar indicated.
IMPACT...Minor hail damage to vegetation is possible.
This strong thunderstorm will be near...
Rochester and Stewartville around 735 PM CDT.
Other locations impacted by this storm include Highway 30 And County
15, Pleasant Grove, Predmore, County Roads 3 And 108, High Forest,
Rock Dell, Rochester Airport, and Simpson.
This includes Interstate 90 in Minnesota between mile markers 202 and
217.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4385 9268 4399 9268 4394 9232 4377 9238
4382 9269 4385 9269
TIME...MOT...LOC 0027Z 286DEG 22KT 4390 9262
MAX HAIL SIZE...0.75 IN
MAX WIND GUST...<30 MPH
SkowThe La Crosse radar (KARX), 109 km away, was scanning. The volume nearest the first event began at 00:34 UTC.
3 hail. Local standard time, as filed.
Broadcaster media reported quarter sized hail 5 miles north-northwest of Stewartville.
The public reported quarter sized hail in Chatfield. The report was relayed via social media.
The public reported quarter sized hail 1 mile east-southeast of Chatfield. The report was relayed via social media.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Minnesota in 2025Every state in 2025This day in weather historyWarnings in Minnesota, August 2025
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: 1289340, 1289341, 1289342.