Scattered afternoon thunderstorms developed along weak convergence in deep cyclonic flow, and despite weak MLCAPE up to 250-500 J/kg, very strong 850-700 hPa winds led to strong outflows on decaying storms with gusts locally 60 to 70 mph.
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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.
Scattered afternoon thunderstorms developed along weak convergence in deep cyclonic flow, and despite weak MLCAPE up to 250-500 J/kg, very strong 850-700 hPa winds led to strong outflows on decaying storms with gusts locally 60 to 70 mph.
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 Jun 17, 12:45 PM CST, 1 hour 34 minutes earlier. Its key messages:
Area Forecast Discussion
National Weather Service Sioux Falls SD
145 PM CDT Wed Jun 17 2026
.KEY MESSAGES...
- Strong northwest winds will continue today with gusts of 40
to 50 mph. A Wind Advisory will be in effect for the entire
area until 9 pm this evening.
- Isolated to scattered showers this afternoon could result in
slightly higher wind gusts (to 60 mph) during the afternoon.
- Isolated showers on Thursday could produce wind gusts to 40
mph.
- Strong to severe storms could return on Saturday along with
locally heavy rain. Specific details are uncertain, but as of
now, the highest probabilities for severe storms remains south
and west of the area.
&&
.DISCUSSION...
Issued at 144 PM CDT Wed Jun 17 2026
A strong jet max continues to wrap around the south side of an upper
level low, bringing strong winds to the area. Peak mixing suggests
that wind gusts could approach 50 mph. Model soundings also indicate
some weaker surface based instability this afternoon, which will
likely generate scattered showers and isolated thunderstorms. The
main concerns from any of this activity will be the potential to mix
down even stronger winds, possibly 60 to 65 mph. These stronger
winds will remain much more isolated.
Thursday will see deep, but weakening northwest flow across the
area. We will likely see a threat for isolated showers with locally
gusty winds to 40 mph as surface based peak mixing CAPE climbs to
about 200 J/kg.
Thursday night into Friday a weak wave will approach and bring some
elevated moisture return and very weak instability. For now any
impacts from this will be very minor.
The next system of interest will come Saturday, but with some
differences from model to model. The 6z EC Ensemble is bringing a 20-
30 percent chance for 2+" of rain to around the Missouri River into
parts of northwest IA while the 12z GFS ensemble and 12z Canadian
ensemble leave these better chances farther south and closer to I-
80. Classically the heavier rain many times falls between roughly
the surface to 850 mb boundary and for now that remains south of the
area, but will need to be monitored in case it drifts north.
Regardless, flooding potential is fairly low as rainfall has been
spotty at best lately.
Below normal temperatures and periodic chances for showers and
thunderstorms are expected Monday through Wednesday next week. A few
shortwaves are expected to move through, with slightly better
chances Monday and Wednesday.
&&
.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1129 AM CDT Wed Jun 17 2026
MVFR ceilings should gradually lift through mid afternoon.
Northwest winds will gust to 45 to 55 mph at times, diminishing
this evening. Scattered showers and isolated thunderstorms
remain likely through the afternoon into the evening and could
produce localized wind gusts to 60 mph as well as very brief
heavy rain.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory until 9 PM CDT this evening for SDZ038>040-050-
052>071.
MN...Wind Advisory until 9 PM CDT this evening for MNZ071-072-080-
081-089-090-097-098.
IA...Wind Advisory until 9 PM CDT this evening for IAZ001>003-
012>014-020>022-031-032.
NE...Wind Advisory until 9 PM CDT this evening for NEZ013-014.
&&
DISCUSSION...08
AVIATION...08Hazardous Weather Outlook National Weather Service Sioux Falls SD 1020 AM CDT Wed Jun 17 2026 IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-NEZ013-014-SDZ038>040-050-052>071-181530- 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- 1020 AM CDT Wed Jun 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...Today and tonight. Strong west to northwest winds are anticipated with gusts averaging 40 and 50 mph at times before weakening this evening. Scattered showers and isolated are expected this afternoon. While severe storms are not anticipated, wind gusts could increase in very localized locations to 50 to 60 mph. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. Though uncertain, thunderstorm risks may increase by late Friday and continue through Saturday. It is uncertain as to if severe storms will be possible. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The Aberdeen radar (KABR), 125 km away, was scanning. The volume nearest the first event began at 20:19 UTC.
5 thunderstorm wind. Local standard time, as filed.
Wind gust measured by South Dakota Road Weather Information System site near Cavour.
Wind gust measured by South Dakota Road Weather Information System site near Forestburg.
Wind gust measured by the South Dakota Road Weather Information System site 4 miles north of Dolton.
Wind gust measured by the South Dakota Road Weather Information System site 4 miles south of Freeman.
Wind gust measured by the South Dakota Road Weather Information System site 4 miles east of Irene.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in South Dakota in 2026Every state in 2026This day in weather historyWarnings in South Dakota, June 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 2026-10-01. Each event’s entry at NCEI: 1346755, 1346756, 1346757, 1346758, 1346759.