Alert archive / Iowa / Severe Thunderstorm Warnings in 2026
Severe Thunderstorm Warning 46, NWS Sioux Falls, SD
NWS Sioux Falls, SD issued this severe thunderstorm warning at May 17, 2026, 6:33 PM CDT for Plymouth County, Sioux County, Iowa. It was in force for 57 min. 4 reports came from inside the area while it was in force.
The area
The outline as issued, with what was reported inside it.
The facts
- Issued
- May 17, 2026, 6:33 PM CDT (23:33 UTC)
- Expired
- May 17, 2026, 7:30 PM CDT
- In force
- 57 min
- Issued by
- NWS Sioux Falls, SD
- Area
- Storm-based polygon
- Hail
- 1.5 in
- Wind
- 60.0 mph
Counties Plymouth County, IA, Sioux County, IA
The radar
The Sioux Falls radar (KFSD), 89 km from the middle of the area, began a volume at 23:36 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
What was reported inside it
| Time | Report | Where | Remark |
|---|---|---|---|
| May 17, 6:43 PM CDT | HAIL 1.75 | 3 Sw Craig, IA | Photo via social media. Time estimated via radar. |
| May 17, 6:43 PM CDT | HAIL 1.75 | 3 Sw Craig, IA | Photo via social media. Time estimated via radar. |
| May 17, 6:50 PM CDT | HAIL 1.25 | Craig, IA | Photo via social media. Time estimated by radar. |
| May 17, 6:50 PM CDT | HAIL 1.25 | Craig, IA | Photo via social media. Time estimated by radar. |
Local storm reports filed while the alert was in force, from inside its polygon or its counties.
Did it verify
Verified. The Iowa Environmental Mesonet's Cow matched 2 storm reports to this severe thunderstorm warning; the first came 10 minutes after it went out.
Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.
The watch it was issued in
The SPC watch in force over the same counties when this warning went out.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| May 17, 1:42 PM CDT | Tornado Watch | SPC | 8 hr |
The nearest sounding before it
Omaha, NE (KOAX), launched 12:00Z, 11.6 hours before the alert went out and 167 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1204 m above ground
- 0-6 km bulk shear
- 49 kt
- 0-1 km storm-relative helicity
- 38 m²/s²
- 0-3 km storm-relative helicity
- -21 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
926
WUUS53 KFSD 172333
SVRFSD
IAC149-167-180030-
/O.NEW.KFSD.SV.W.0046.260517T2333Z-260518T0030Z/
BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Sioux Falls SD
633 PM CDT Sun May 17 2026
The National Weather Service in Sioux Falls has issued a
* Severe Thunderstorm Warning for...
South central Sioux County in northwestern Iowa...
Northwestern Plymouth County in northwestern Iowa...
* Until 730 PM CDT.
* At 633 PM CDT, a severe thunderstorm was located near Akron, or 13
miles south of Hawarden, moving northeast at 20 mph.
HAZARD...Ping pong ball size hail and 60 mph wind gusts.
SOURCE...Radar indicated.
IMPACT...People and animals outdoors will be injured. Expect hail
damage to roofs, siding, windows, and vehicles. Expect
wind damage to roofs, siding, and trees.
* This severe thunderstorm will be near...
Craig around 640 PM CDT.
Other locations in the path of this severe thunderstorm include
Ireton, Struble, Le Mars and Maurice.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Prepare immediately for large hail and deadly cloud to ground
lightning. Seek shelter inside a well-built structure. Stay away from
windows.
A Tornado Watch remains in effect until 1000 PM CDT for northwestern
Iowa...and southeastern South Dakota.
&&
LAT...LON 4269 9651 4281 9659 4284 9658 4284 9655
4288 9655 4304 9622 4276 9607
TIME...MOT...LOC 2333Z 244DEG 19KT 4280 9650
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.50 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH
$$
BP2 follow-up statements
608
WWUS53 KFSD 172351
SVSFSD
Severe Weather Statement
National Weather Service Sioux Falls SD
651 PM CDT Sun May 17 2026
IAC149-167-180030-
/O.CON.KFSD.SV.W.0046.000000T0000Z-260518T0030Z/
Sioux IA-Plymouth IA-
651 PM CDT Sun May 17 2026
...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 730 PM CDT
FOR SOUTH CENTRAL SIOUX AND NORTH CENTRAL PLYMOUTH COUNTIES...
At 651 PM CDT, a severe thunderstorm was located over Craig, or 9
miles northwest of Le Mars, moving northeast at 30 mph.
HAZARD...Two inch hail and 60 mph wind gusts.
SOURCE...Radar indicated.
IMPACT...People and animals outdoors will be injured. Expect hail
damage to roofs, siding, windows, and vehicles. Expect wind
damage to roofs, siding, and trees.
Locations impacted include...
Ireton, Maurice and Struble.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
A Tornado Watch remains in effect until 1000 PM CDT for northwestern
Iowa.
Prepare immediately for large hail and deadly cloud to ground
lightning. Seek shelter inside a well-built structure. Stay away from
windows.
&&
LAT...LON 4278 9639 4287 9640 4293 9640 4304 9622
4281 9610
TIME...MOT...LOC 2351Z 241DEG 25KT 4289 9627
THUNDERSTORM DAMAGE THREAT...CONSIDERABLE
HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...2.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH
$$
BP449
WWUS53 KFSD 180033
SVSFSD
Severe Weather Statement
National Weather Service Sioux Falls SD
733 PM CDT Sun May 17 2026
IAC149-167-180043-
/O.EXP.KFSD.SV.W.0046.000000T0000Z-260518T0030Z/
Sioux IA-Plymouth IA-
733 PM CDT Sun May 17 2026
...THE SEVERE THUNDERSTORM WARNING FOR SOUTH CENTRAL SIOUX AND NORTH
CENTRAL PLYMOUTH COUNTIES HAS EXPIRED...
The storm which prompted the warning has moved out of the area.
Therefore, the warning has been allowed to expire.
A Tornado Watch remains in effect until 1000 PM CDT for northwestern
Iowa.
To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
Sioux Falls.
&&
LAT...LON 4278 9639 4287 9640 4293 9640 4304 9622
4281 9610
TIME...MOT...LOC 0033Z 244DEG 19KT 4299 9600
$$
BPWhat forecasters said that day
The local office's own words before this severe thunderstorm warning went out, 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 this severe thunderstorm warning went out at May 17, 1:20 PM CDT, 5 hours 13 minutes earlier. Its 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.
Area forecast discussion, May 17, 1:20 PM CDT, 5 hours 13 minutes before
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, May 17, 1:29 PM CDT, 5 hours 4 minutes before
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.
In the hours before
Local storm report, May 17, 6:02 PM CDT, 31 minutes before
Preliminary Local Storm Report
National Weather Service Sioux Falls SD
602 PM CDT Sun May 17 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0551 PM Hail Rock Valley 43.20N 96.30W
05/17/2026 M0.75 Inch Sioux IA Public
mPING: Dime (0.75 in.). Time estimated via
radar.
&&
akLocal storm report, May 17, 6:05 PM CDT, 28 minutes before
Preliminary Local Storm Report
National Weather Service Sioux Falls SD
605 PM CDT Sun May 17 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0544 PM Tstm Wnd Gst 4 NE Adrian 43.68N 95.89W
05/17/2026 M62 MPH Nobles MN Public
Via personal weather station. Exact time
estimated via radar.
&&
akLocal storm report, May 17, 6:16 PM CDT, 17 minutes before
Preliminary Local Storm Report
National Weather Service Sioux Falls SD
616 PM CDT Sun May 17 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0409 PM Tstm Wnd Dmg 3 E Parker 43.39N 97.08W
05/17/2026 Turner SD Public
Power poles snapped and irrigation pivots
flipped near the intersection of 276th St
and 456th Ave. Time estimated from radar.
&&
PRLocal storm report, May 17, 6:19 PM CDT, 14 minutes before
Preliminary Local Storm Report
National Weather Service Sioux Falls SD
619 PM CDT Sun May 17 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0615 PM Tornado 3 SW Worthington 43.60N 95.64W
05/17/2026 Nobles MN Trained Spotter
Unconfirmed report of tornado approximately
1 mile southwest of Worthington. Debris
currently being observed.
&&
akLocal storm report, May 17, 6:24 PM CDT, 9 minutes before
Preliminary Local Storm Report
National Weather Service Sioux Falls SD
624 PM CDT Sun May 17 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0618 PM Hail 5 SW Worthington 43.57N 95.65W
05/17/2026 M1.00 Inch Nobles MN Public
Report from mPING: Time estimated via radar.
&&
akLocal storm report, May 17, 6:33 PM CDT, 0 minutes before
Preliminary Local Storm Report
National Weather Service Sioux Falls SD
633 PM CDT Sun May 17 2026
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0601 PM Tstm Wnd Gst Florence 44.24N 96.05W
05/17/2026 M60 MPH Lyon MN Mesonet
Mesonet station MN160 U.s.14 - Florence - Mp
21.2. Time estimated via radar.
&&
akThe office that day
Everything else NWS Sioux Falls, SD issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 16, 11:14 PM CDT | Severe Thunderstorm Warning | FSD | Clay, O'Brien | 16 min |
| May 17, 1:10 AM CDT | Flash Flood Warning | FSD | Plymouth | 4 hr |
| May 17, 4:18 PM CDT | Severe Thunderstorm Warning | FSD | Lyon | 42 min |
| May 17, 4:27 PM CDT | Tornado Warning | FSD | Lyon | 48 min |
| May 17, 4:56 PM CDT | Severe Thunderstorm Warning | FSD | Lyon | 49 min |
| May 17, 5:43 PM CDT | Severe Thunderstorm Warning | FSD | Lyon, Osceola | 62 min |
| May 17, 5:56 PM CDT | Severe Thunderstorm Warning | FSD | Lyon, O'Brien, Osceola, Sioux | 27 min |
| May 17, 6:30 PM CDT | Severe Thunderstorm Warning | FSD | Dickinson, Osceola | 75 min |
Nearby
Severe Thunderstorm Warnings in Iowa, 2026Every severe thunderstorm warning in 2026
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.