Strong warm advection ahead of an approaching northwest flow wave spawned several elevated thunderstorms, some of which organized into short bowing segments with 60 to 70 knots of effective shear and around 2000 J/kg MUCAPE. Convective wind gusts from 58 to 68 mph occurred near the Storm Lake area.
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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.
Strong warm advection ahead of an approaching northwest flow wave spawned several elevated thunderstorms, some of which organized into short bowing segments with 60 to 70 knots of effective shear and around 2000 J/kg MUCAPE. Convective wind gusts from 58 to 68 mph occurred near the Storm Lake area.
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, 2:07 AM CST, 25 minutes earlier. Its key messages:
Area Forecast Discussion
National Weather Service Sioux Falls SD
307 AM CDT Wed Jun 17 2026
.KEY MESSAGES...
- Periods of scattered showers with isolated thunderstorms
continue into the overnight hours. An isolated strong to
severe storm is possible along and east of Iowa/Minnesota
Highway 60 between 4 am and 7 am. Large hail to the size of a
half dollar (1.25") is possible.
- Strong northwest winds are expected Wednesday with gusts of 45
to 55 mph. A Wind Advisory will be in effect for the entire
area from 10 am to 9 pm on Wednesday. Another round of
isolated to scattered showers could result slightly higher
wind gusts (to 60 mph) during the afternoon.
- The next potential chance for strong to severe storms could
return on Saturday. Specific details are uncertain but as of
now, the highest probabilities for severe storms remains south
and west of the area.
&&
.UPDATE...
Issued at 305 AM CDT Wed Jun 17 2026
No major changes made to the forecast over the upcoming 12-24 hours.
Low-lvl flow continues to increase this morning, with VWP
showing 50+ knot winds at FSD/OAX this morning. Instability has
been a bit slower to arrive than suggested by the RAP as strong
moisture transport has lagged. Soundings from the HRRR/GFS/NAM
all showing some minor inhibition lingering over NW Iowa from
any parcel lifted at 800 mb where the greatest concentration of
low- lvl convergence exists. However, if we can erode this
inhibition, then a few stronger storms remain possible through
7am over NW Iowa and southern Minnesota before the wave pushes
through the CWA. Large hail remains the greatest risk. The
threat will move east of the CWA by 7am with the passage of the
wave and veering of the LLJ.
Strong northwest wind remain on target to arrive into South Central
SODAK by 8am and will spread eastward through the day. Soundings
show potential for scattered 50+ mph wind gusts, so advisory remains
valid. Given dry conditions through the Missouri and James river
valley, locally elevated fire danger will be possible this
afternoon. It may not take long into the day for scattered
showers and thunderstorms to develop over northern South Dakota and
track southeast during the day given increasing low-lvl lapse
rates.
&&
.DISCUSSION...
Issued at 226 PM CDT Tue Jun 16 2026
Starting to see some echoes on radar begin to move into the forecast
area from central South Dakota this afternoon as we begin to see an
upper level wave push into the Northern Plains. With dry air in the
low levels, little if any rain will reach the surface. Could see an
isolated wind gust up to 30-40 mph as the showers push through. The
main forcing from the wave will come during the overnight hours
which will increase the coverage of showers and some storms. Latest
hi-res guidance shows a strengthening low level jet (LLJ) that will
bring a small elevated moist layer northwards. This moist layer will
push into locations around highway-60 eastwards. This will be a
brief window where weak elevated instability on the order of about
300 to 500 J/kg of CAPE can be generated and support the potential
for an isolated severe storm. The timeframe is between 4 am to 7 am.
Large hail up to quarter size is possible. These showers will
continue to push off to the southeast and begin exiting the area
through tomorrow morning.
A cold front will push through the area early Wednesday morning. A
strong push of cold air advection (CAA) will accompany the cold
front. Despite the CAA, highs look to warm to the 70s and 80s. The
main impact from the CAA will be strong northwest winds. Winds will
gust up to 45-55 mph Wednesday afternoon across the entire area. As
such, a Wind Advisory has been issued for the entire forecast area
from 10 am to 9 pm. Another round of isolated to scattered showers
is on the table as well for Wednesday afternoon. Isolated higher
wind gusts are possible within these showers. Elevated fire danger
is possible across south central South Dakota where the humidity
will be lowest. The shower activity will be waning through the
evening along with the strong wind gusts.
Thursday and Friday will be relatively quieter days with high
pressure pushing through the area. High temperatures will warm to
the 70s and 80s. A few showers are possible on both days but
otherwise the days should largely be dry. Low temperatures will fall
to the upper 40s, 50s, and low 60s. The warmest lows will come
Friday night.
Upper level troughing will be pushing eastwards on Saturday, putting
the right entrance region over the forecast area. This looks to
bring a warm front near the Missouri River valley. Medium range
guidance has the surface warm front south and west of the forecast
area. The ensembles also support this as they also show the surface
front residing south and west of the forecast area. The vast
majority of machine learning guidance (ML) further supports this
conclusion as well. That said, this is the surface front location.
Can't rule out the potential for elevated storms though it is too
far out to say for sure if the elevated boundary may make it to near
the Missouri River Valley. The ensembles also show the highest
probabilities (60-80%) for rainfall amounts exceeding a tenth of an
inch south and west of the Missouri River as well. Aside from storm
chances, Saturday looks to be a near seasonable day with highs in
the upper 70s and 80s.
Zonal flow looks to take over for Sunday and Monday. This could
result in additional chances for rain but this remains uncertain due
to the variance in shortwave troughs evolution among the medium
range guidance. The ensembles reflect this uncertainty as they only
show a 20-40% chance for rainfall amounts to exceed a tenth of an
inch on both days. Otherwise temperatures look to remain near
seasonable in the 70s.
&&
.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1216 AM CDT Wed Jun 17 2026
Outside of convection, VFR conditions prevail through the
period. Have seen a few sites over the last hour drop to MVFR
conditions with lower stratus and heavy rainfall in stronger
showers. Showers and isolated thunderstorms continue moving
southeast through the early morning hours. Have added some
prevailing -SHRA and mentioned -TSRA in TEMPO/PROB30 groups at
all three sites given the more isolated nature of TS (KHON and
KFSD) and lower confidence in occurrence (KSUX). Additional
showers and isolated storms are expected Wednesday
afternoon/evening, with the greatest chances northeast of KHON-
KFSD-KSPW. Therefore, limited mention at KHON/KFSD and omitted
TS.
Southerly winds early this morning shift northwesterly and
increase quickly behind a front. With gusts continuing around 20
knots overnight, have continued to omit LLWS as the LLJ
strengthens due to marginal speed shear. Directional shear will
exceed 30 degrees at times with directional shifts. Wind gusts
through most of the day fall in the 30-40 knot range, with
higher gusts in south central SD. Winds taper down after sunset.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory from 1 PM this afternoon to 9 PM CDT this
evening for SDZ040-056-062-067-071.
Wind Advisory from 10 AM this morning to 9 PM CDT this evening
for SDZ038-039-050-052>055-057>061-063>066-068>070.
MN...Wind Advisory from 1 PM this afternoon to 9 PM CDT this
evening for MNZ071-072-080-081-089-090-097-098.
IA...Wind Advisory from 1 PM this afternoon to 9 PM CDT this
evening for IAZ001>003-012>014-020>022-031-032.
NE...Wind Advisory from 1 PM this afternoon to 9 PM CDT this
evening for NEZ014.
Wind Advisory from 10 AM this morning to 9 PM CDT this evening
for NEZ013.
&&
UPDATE...Dux
DISCUSSION...Meyers
AVIATION...SGHazardous Weather Outlook National Weather Service Sioux Falls SD 230 AM CDT Wed Jun 17 2026 MNZ071-072-097-098-NEZ013-SDZ038>040-050-052>071-180730- Lincoln-Lyon-Pipestone-Rock-Dixon-Beadle-Kingsbury-Brookings-Gregory- Jerauld-Sanborn-Miner-Lake-Moody-Brule-Aurora-Davison-Hanson-McCook- Minnehaha-Charles Mix-Douglas-Hutchinson-Turner-Bon Homme-Yankton- Clay-Union- 230 AM CDT Wed Jun 17 2026 This Hazardous Weather Outlook is for southwest Minnesota, northeast Nebraska, central South Dakota, east central South Dakota, south central South Dakota and southeast South Dakota. .DAY ONE...Today and tonight. Showers and thunderstorms will continue through daybreak. Severe storms are not anticipated, however a few storms could produce brief gusty winds and small hail. Wind gusts between 40 and 50 mph will be possible through the day on Wednesday. Winds will gradually weaken this evening. Scattered showers and isolated thunderstorms will redevelop by mid- day and continue into the evening. While severe storms are not expected, smaller hail and localized stronger winds are possible. .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. IAZ001>003-012>014-020>022-031-032-MNZ080-081-089-090-NEZ014-180730- Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee- Buena Vista-Woodbury-Ida-Murray-Cottonwood-Nobles-Jackson-Dakota- 230 AM CDT Wed Jun 17 2026 This Hazardous Weather Outlook is for northwest Iowa, west central Iowa, southwest Minnesota and northeast Nebraska. .DAY ONE...Today and tonight. Scattered stronger thunderstorms may begin to develop by 4 am in portions of southern Minnesota and northwest Iowa and continue through 7am. The primary risks will be ping pong ball size hail. Strong west to northwest winds are anticipated from mid-morning Wednesday into Wednesday evening. Gusts may range between 40 and 50 mph at times before weakening this evening. A few scattered showers and thunderstorms may develop this afternoon. Severe storms are not anticipated. .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 Sioux Falls radar (KFSD), 158 km away, was scanning. The volume nearest the first event began at 08:32 UTC.
2 thunderstorm wind. Local standard time, as filed.
Wind gust measured by the Iowa Road Weather Information System site 2 miles northeast of Truesdale.
Thunderstorm wind gust measured by AWOS station KSLB near Storm Lake.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2026Every state in 2026This day in weather historyWarnings in Iowa, 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 2026-09-24. Each event’s entry at NCEI: 1346707, 1346716.