In advance of a deep mid-level trough pushing eastward out of the Rockies, a weakening line of thunderstorms moved northeast across the Northern Plains in the early morning hours. A large and dwindling stratiform area supported the development of a strong wake low with wind gusts as high as 70 to 75 mph in portions of southeast South Dakota as well as northwest Iowa.
Every event with a place to put it; 7 filed by county or forecast zone are drawn at its center, in a lighter ring. 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 FSD wrote it up.
In advance of a deep mid-level trough pushing eastward out of the Rockies, a weakening line of thunderstorms moved northeast across the Northern Plains in the early morning hours. A large and dwindling stratiform area supported the development of a strong wake low with wind gusts as high as 70 to 75 mph in portions of southeast South Dakota as well as northwest Iowa. Sporadic tree and building damage were reported as well as numerous power outages, which left around 630 customers without power during the early morning hours along the Interstate 29 corridor in South Dakota and almost 1600 without power in parts of northwest Iowa.
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 19, 2:32 AM CST, 1 hour 58 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Sioux Falls SD 332 AM CDT Mon May 19 2025 .KEY MESSAGES... - Isolated severe storms will be possible into mid morning. Hail to the size of quarters will be the main concern. - Strong wind gusts in excess of 50 mph may be possible behind these storms before they exit to the northeast by mid morning. - A few severe storms will again be possible this afternoon and evening, with the better chances in northeast NE and northwest IA. Hail, wind and and isolated tornado are all possible, although the tornado threat may remain just south of the area if the near surface front does not get far enough north. - Periods of rain and isolated thunderstorms continue into Wednesday. Still some question marks on rainfall totals, but pockets of 2-3 inches are likely. While this may cause some local rises in small streams and creeks, flash flooding is not anticipated. - After a break on Thursday, rain and thunderstorm chances return for Friday into the beginning of next week. && .DISCUSSION... Issued at 330 AM CDT Mon May 19 2025 NOW THROUGH WEDNESDAY: Elevated showers with isolated lightning strikes continue to lift to the northeast across the area very early this morning. This out ahead of an upper level trough tracking eastward out of the Rockies and a surface low and attendant boundaries over western Nebraska - with moisture being provided by a 40 to 50 kt low level jet (LLJ) over our area. Current SPC mesoanalysis indicates any appreciable instability and effective shear remaining to the south of our CWA. However, model guidance would suggest elevated instability on the order of 500-1000 J/KG lifting into our area toward daybreak. With effective shear around 30 kts and mid level lapse rates of 7-8 deg C/KM cannot rule out an isolated severe storm with hail to the size of quarters through at least mid morning, before lifting to the northeast with the associated mid level frontogenesis. Wind is a lesser threat with a low level inversion in place. In spite of an inversion, there is at least some concern for the potential of strong easterly winds (possibly 50+ mph) mixing down from the LLJ on the backside of the showers and storms. Nearly every hi- res model shows this potential to some degree - with the HRRR and ARW being the strongest with these winds. That being said, model soundings are less bullish on mixing these gusts down, though it will be something to keep an eye on through the morning hours. Scattered showers and storms will periodically continue through the day as the mid/upper low and trough axis pivots into the northern Plains and the LLJ meanders toward Minnesota. Surface low tracks north through NE during the day. Guidance indicates that we'll see an increase in instability, but also more a little more capping. If we're able to see efficient moisture return with the easterly and southeasterly flow and we're not inhibited by convection to our south, could see a few strong to severe storms near and east of US Hwy 81 during the afternoon and evening hours where instability is highest (over 1500 J/kg). Think that large hail remains the main threat, with damaging wind gusts as the secondary threat. If the surface warm front can move this far north through the day, a tornado may be possible near the boundary - though there is a greater chance of this boundary remaining to the south of our CWA. Showers and storms continue through Tuesday as the low pressure moves off to the east and northwesterly flow aloft remains in place. By Wednesday morning, still expect another area of mid/upper low pressure to develop to our east, which maintains our rain and storm chances through the day Wednesday. Temperatures remain below normal with strong winds through Tuesday night. Easterly winds become northwesterly behind the surface low exiting our area Tuesday and remain breezy Wednesday. Some uncertainty in rainfall totals through this event, mainly stemming from the potential for our moisture return to be cut off by severe weather to our south. Probabilities across the area for over an inch of rain are still high (over 80%); however, believe that ensembles are washing out the nuances of the convection. Some areas could see more than 2" (ensemble probabilities 50-65% for the James Valley and east of I-29), with deterministic guidance showing some locations approaching 3" or more. Given the duration of the event, shouldn't see much in the way of flooding, though heavier rain could lead to localized ponding. THURSDAY: Dry and cool Thursday with weak ridging in place and northwesterly flow aloft. Highs in the 60s. LATE WEEK INTO NEXT WEEKEND: Unsettled weather returns for the end of the week and the weekend as short wave moves through the mid levels followed by troughing for the weekend. Periods of showers and storms return with slightly below average temperatures. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1035 PM CDT Sun May 18 2025 First push of showers and scattered thunderstorms is making its way through the MO and James River Valleys as of 03z, and expect them to continue northeast through the overnight. VFR conditions will give way to MVFR/IFR conditions as multiple rounds of showers and storms work through the area. Some breaks in convection are expected, but there remains uncertainty in time, so have left prevailing showers in for most of the period. A few storms could be strong to severe, with hail the main threat. Guidance indicates that there may be stronger easterly winds behind showers/storms overnight and toward daybreak Monday (over 45 knots), but not confident enough in timing/potential for mention. Otherwise, strong easterly winds prevail through Monday night with gusts around 35 knots. Gusts begin to taper toward the end of the period, but remain breezy. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && DISCUSSION...JM/SG AVIATION...SG
Hazardous Weather Outlook National Weather Service Sioux Falls SD 402 AM CDT Mon May 19 2025 IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-NEZ013-014-SDZ038>040-050-052>071-200915- 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- 402 AM CDT Mon May 19 2025 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...Today and tonight. Isolated thunderstorms will be capable of producing hail to the size of quarters through mid morning, along with pockets of heavy rain. On the back side of the storms there is a risk of wind gusts of 50 to 60 mph. Additional storms could become strong to severe this afternoon and evening. The main threats would be large hail and damaging winds, with an isolated tornado risk mainly along and south of highway 20 in northwestern Iowa. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Showers and isolated thunderstorms will continue on Tuesday and Wednesday. Total rainfall amounts of 1 to 3 inches will be possible for the period of Monday through Wednesday. .SPOTTER INFORMATION STATEMENT... Spotter activation is possible.
Special Weather Statement National Weather Service Sioux Falls SD 435 AM CDT Mon May 19 2025 SDZ038>040-052>070-191200- Beadle-Kingsbury-Brookings-Jerauld-Sanborn-Miner-Lake-Moody-Brule- Aurora-Davison-Hanson-McCook-Minnehaha-Charles Mix-Douglas- Hutchinson-Turner-Lincoln-Bon Homme-Yankton-Clay- Including the cities of Huron, De Smet, Arlington, Lake Preston, Brookings, Wessington Springs, Alpena, Woonsocket, Howard, Madison, Orland, Flandreau, Chamberlain, Kimball, Plankinton, White Lake, Stickney, Mitchell, Alexandria, Emery, Salem, Canistota, Bridgewater, Montrose, Sioux Falls, Wagner, Platte, Lake Andes, Marty, Armour, Corsica, Delmont, Parkston, Freeman, Menno, Tripp, Clayton, Parker, Centerville, Marion, Viborg, Irene, Hurley, Chancellor, Canton, Lennox, Tea, Harrisburg, Tyndall, Scotland, Springfield, Avon, Tabor, Yankton, and Vermillion 435 AM CDT Mon May 19 2025 ...Gusty Winds Associated With Showers... Winds gusts of 45 to 55 mph will be possible on the back side of showers as they move to the northeast across the area through 7 am. Loose objects may be blown around and high profile vehicles may be impacted by these stronger winds.
The national radar mosaic for the moment the first event began.
4 high wind, 3 strong wind. Local standard time, as filed.
Sustained easterly winds knocked down several large trees in Remsen with significant tree damage in Akron. Wind speeds were estimated at 60 to 65 mph.
Sustained easterly winds reached 33 to 39 mph with gusts as high as 61 mph at Moville.
Sustained easterly winds reached 45 to 54 mph with gusts as high as 73 mph 6 miles west of Rock Valley, 64 mph 4 miles west of Sheldon and 4 miles southeast of Hawarden, and 58 mph near Hull. Significant damage occurred to large trees in Hawarden and Rock Valley, and the roof was peeled off a local business in Hawarden.
Sustained easterly winds reached 45 to 53 mph with gusts as high as 72 mph 4 miles east of Lester, 63 mph 4 miles east of Rock Rapids, 63 mph at Rock Rapids, and 62 mph at Larchwood. Significant damage was reported with numerous large trees down in Alvord, Doon, and Rock Rapids.
Sustained easterly winds reached 30 to 37 mph with gusts as high as 54 mph at Sibley.
Sustained easterly winds reached 30 to 38 mph with gusts as high as 48 mph at Sheldon.
Sustained easterly winds reached 30 to 33 mph at Marcus.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2025Every state in 2025This day in weather historyWarnings in Iowa, May 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: 1268424, 1268428, 1268427, 1268419, 1268430, 1268431, 1268435.