An approaching mid-level disturbance broke a weak cap and allowed storms to erupt during the afternoon along a slow moving frontal boundary. These storms rapidly organized into short bowing segments and then became highly linear across northwest Iowa and southwest Minnesota during the evening.
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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 FSD wrote it up.
An approaching mid-level disturbance broke a weak cap and allowed storms to erupt during the afternoon along a slow moving frontal boundary. These storms rapidly organized into short bowing segments and then became highly linear across northwest Iowa and southwest Minnesota during the evening. Initial supercell storms produced large hail with as much as 2000-3000 J/kg MLCAPE, but DCAPE of around 750-1000 J/kg allowed for the development of organized cold pools and an increasing wind threat. Several brief and highly visible tornadic spin-ups developed along the line of storms by late afternoon and evening across far eastern South Dakota, northwest Iowa and southwest Minnesota.
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 Sioux Falls, SD wrote its last area forecast discussion before the first event at May 17, 12:20 PM CST, 3 hours 58 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Sioux Falls SD Issued by National Weather Service Lincoln IL 120 PM CDT Sun May 17 2026 .KEY MESSAGES... - There is high confidence that severe thunderstorms will develop this afternoon and evening, producing large hail, destructive straight-line winds, and a few tornadoes. An Enhanced Risk (level 3 of 5) of severe storms is in place. - A transitioning storm mode will shift hazards from large hail and tornadoes initially, to widespread wind damage as an intense line of storms tracks east of Interstate 29 this evening. - A lower risk of severe weather exists late Monday afternoon and evening, mainly over northwest IA, before quieter weather moves in for the mid-week period. && .DISCUSSION... Issued at 120 PM CDT Sun May 17 2026 The short-term convective outlook presents a highly volatile spring severe weather setup. Latest surface analysis shows a complex pattern, anchored by a strong 994 mb low over northwest KS. An inverted trough extended north of the low through central SD, while a well-defined warm front stretched northeast of the low into east central NE. A weaker low was also noted in north central NE. Visible satellite imagery revealed stable wave clouds advancing northeast over far northeast NE and extreme SE SD, ahead of the advancing warm front. Regional radar imagery showed a complex of strong to severe storms over north central NE. This storm complex is forecast by short range guidance to continue tracking east this afternoon, intensifying as interacts with the richer low- level moisture pool near and south of the warm front. Moderate to strong instability will be in place over the southern to eastern CWA by late afternoon with MLCAPE nearing 3000 J/kg. In addition, deep layer shear will increase to around 50 kt, coincident with a mid level speed max ejecting from the deep upper trough to our west. As the system evolves over the next several hours, it appears the ingredients for a significant severe weather event will be most favored over the southern to eastern CWA. Ahead of the main convective line, some CAMs show supercell development along the northward advancing warm front. These storms would present a risk of very large hail (2"+) and tornadoes. Given the amount of low level SRH/curved hodographs present, a couple strong tornadoes are possible. The convective cluster currently entering our far southwest CWA should strengthen as it shifts east, with an initial hail and tornado threat transitioning to a damaging straight line wind threat (70+ MPH) as it grows upscale into a squall line/QLCS. Some line-embedded QLCS tornadoes are possible, especially for any line segments that become oriented north/south or northwest/southeast, given southwesterly 0-3 km shear vectors. Timing from latest high-res guidance suggests this activity exits to the east of our CWA late this evening. Precipitation amounts will vary significantly based on convective tracks, though NBM guidance and HREF probability match mean fields project a widespread 0.50 to 1.50 inches of rainfall, particularly across northwest Iowa and southwest Minnesota. On Monday, the cold front finally pushes into the area. Instability and shear are forecast to be much lower than today, however, there will be a conditional risk of severe storms over the eastern CWA during the late afternoon to evening, if the airmass can destabilize sufficiently ahead of the front. SPC's Day 2 outlook indicates as Marginal Risk (level 1 of 5), for our MN and IA counties. Behind the departing upper wave, quasi-zonal flow sets up for Tuesday and Wednesday, yielding quiet conditions and seasonally cool high temperatures moderating from the upper 50s Tuesday to mid-upper 60s Wednesday. The next upper wave moves in for the Thursday to Friday period, however Gulf moisture remains cutoff ahead of this system. Evaluating the ECMWF Extreme Forecast Index (EFI) reveals no significant climatological anomalies for precipitation or wind across the upper Midwest during this period, reinforcing the the idea of a low-impact system for our area. The current forecast sticks closely to the NBM consensus, maintaining broad 20-30 percent probabilities for light rain for late Thursday into Saturday. By late this week and especially this weekend, temperatures will embark on a steady upward trajectory, as the mid level flow backs west, then southwest. The Climate Prediction Center (CPC) 6-10 day outlook favors above-normal temperatures across the Northern Plains and Upper Midwest, which supports blended guidance high temperatures reaching well into the 80s on Sunday. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1248 PM CDT Sun May 17 2026 Showers and storms move through the region this afternoon into tonight. Intermittent MVFR/IFR conditions will be possible throughout this timeframe, especially in heavier rain. TSRA was included at least in PROB30 groups, but is expected to be the dominant weather type at times. Widespread MVFR/IFR cigs setting in overnight for much of Monday. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && DISCUSSION...ILX/25 AVIATION...DYE
Hazardous Weather Outlook National Weather Service Sioux Falls SD Issued by National Weather Service Lincoln IL 129 PM CDT Sun May 17 2026 IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-NEZ013-014-SDZ038>040-050-052>071-181830- Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee- Buena Vista-Woodbury-Ida-Lincoln-Murray-Cottonwood-Nobles-Jackson- Pipestone-Rock-Dixon-Dakota-Beadle-Kingsbury-Brookings-Gregory- Jerauld-Sanborn-Miner-Lake-Moody-Brule-Aurora-Davison-Hanson-McCook- Minnehaha-Charles Mix-Douglas-Hutchinson-Turner-Bon Homme-Yankton- Union- 129 PM CDT Sun May 17 2026 This Hazardous Weather Outlook is for northwest Iowa, west central Iowa, southwest Minnesota, northeast Nebraska, central South Dakota, east central South Dakota, south central South Dakota and southeast South Dakota. .DAY ONE...This afternoon and tonight. A significant severe weather event is possible this afternoon and evening. Very large hail, damaging wind gusts, and tornadoes are all possible. If you have outdoor plans know where your nearest shelter is located. Please ensure you have multiple ways to receive warnings. Have a plan to take shelter and act immediately if your area comes under a severe weather warning. .DAYS TWO THROUGH SEVEN...Monday through Saturday. Strong to severe storms are possible again Monday afternoon and evening, particularly over northwest Iowa and southwest Minnesota. .SPOTTER INFORMATION STATEMENT... Spotter activation will likely be needed this afternoon and evening.
Preliminary Local Storm Report
National Weather Service Sioux Falls SD
437 PM CDT Sun May 17 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0432 PM Hail 5 W Sioux Falls 43.53N 96.84W
05/17/2026 E1.00 Inch Minnehaha SD Public
Report from mPING.
&&
akPreliminary Local Storm Report
National Weather Service Sioux Falls SD
440 PM CDT Sun May 17 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0417 PM Tstm Wnd Gst 2 ENE Chancellor 43.39N 96.94W
05/17/2026 M70 MPH Turner SD Public
Via personal weather station. Exact time
estimated via radar.
&&
akPreliminary Local Storm Report
National Weather Service Sioux Falls SD
441 PM CDT Sun May 17 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0414 PM Tstm Wnd Gst 1 S Chancellor 43.36N 96.99W
05/17/2026 M60 MPH Turner SD Public
Via personal weather station. Exact time
estimated via radar.
&&
akPreliminary Local Storm Report
National Weather Service Sioux Falls SD
444 PM CDT Sun May 17 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0436 PM Hail 4 NW Harrisburg 43.48N 96.75W
05/17/2026 M1.00 Inch Lincoln SD Emergency Mngr
Report from 85th and Western of quarter size
hail.
&&
akPreliminary Local Storm Report
National Weather Service Sioux Falls SD
449 PM CDT Sun May 17 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0438 PM Hail Tea 43.45N 96.84W
05/17/2026 M1.00 Inch Lincoln SD Public
&&
THPreliminary Local Storm Report
National Weather Service Sioux Falls SD
452 PM CDT Sun May 17 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0447 PM Hail 4 SSE Sioux Falls 43.49N 96.71W
05/17/2026 M1.50 Inch Lincoln SD Trained Spotter
&&
MMThe Sioux Falls radar (KFSD), 28 km away, was scanning. The volume nearest the first event began at 22:21 UTC.
8 hail, 5 thunderstorm wind, 2 tornado. Local standard time, as filed.
Thunderstorm wind gusts measured by the Minnesota Road Weather Information System site near Beaver Creek.
Thunderstorm wind gust was measured by the AWOS station KLYV 3 miles south of Luverne.
Thunderstorm wind gusts measured by a personal weather station.
A brief tornado occurred in an open field around 6 miles south of Rushmore. The tornado was estimated to touch down around one-half mile northwest of the intersection of 320th Street and Jones Avenue. The tornado tracked northeast for less than two minutes across open fields before lifting south of 310th Street west of King Avenue. There were no damage indicators present to derive a rating. The average path width was estimated at 25 yards based on video evidence.
Thunderstorm wind gusts measured by the Minnesota Road Weather Information System site near Florence.
A trained spotter observed a very brief tornado in an open field southwest of Worthington. The tornado was estimated to touch down just east of Oliver Avenue around one-half mile north of 280th Street. The tornado tracked northeast in open fields for less than one minute before lifting near South Crailsheim Road. There were no damage indicators present to derive a rating. The average path width was estimated at 20 yards.
Thunderstorm wind gust measured by a personal weather station.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Minnesota in 2026Every state in 2026This day in weather historyThe tornado archive for Minnesota, 2026Warnings in Minnesota, May 2026
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: 1343927, 1343928, 1343899, 1343929, 1343901, 1343907, 1343849, 1343914, 1343930, 1343836, 1343911, 1343920, 1343922, 1343932, 1343924.