As a subtle mid-level impulse worked eastward across the region, a couple of multicell thunderstorm clusters developed during the early to mid afternoon across northwest Iowa near and to the north of the surface boundary. With mixed-layer instability of 1500-2000 J/kg and deep-layer shear of 35-40 knots, organized storms developed and utilized an inverted-V thermodynamic profile to accentuate a…
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The episode as NWS FSD wrote it up.
As a subtle mid-level impulse worked eastward across the region, a couple of multicell thunderstorm clusters developed during the early to mid afternoon across northwest Iowa near and to the north of the surface boundary. With mixed-layer instability of 1500-2000 J/kg and deep-layer shear of 35-40 knots, organized storms developed and utilized an inverted-V thermodynamic profile to accentuate a swath of damaging wind gusts near and just south of Iowa State Highway 9.
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 11, 11:55 AM CST, 31 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Sioux Falls SD 1255 PM CDT Wed Jun 11 2025 .KEY MESSAGES... - Morning showers and isolated storms continue, with increased risks for thunderstorms south of I-90 today between 2 pm and 10 pm. Isolated strong to severe storms possible, with large hail (up to 1.5") and strong wind gusts (60-70 mph). - Thunderstorm risks continue tonight into Thursday morning, slowly shifting northward. Persistent marginal large hail risks along with the potential for locally heavy rainfall are expected. Exact locations remain uncertain, though favor areas along/north of I-90. - More of the same Thursday into Thursday night with isolated to scattered severe storms possible in the afternoon and evening; exact area remains uncertain. Locally heavy rainfall risk continues. - Temperatures rise through the upcoming weekend, bringing additional thunderstorm risks by Sunday and into next week. Monitor for strong storm potential. && .DISCUSSION... Issued at 351 AM CDT Wed Jun 11 2025 TODAY: Showers and isolated thunderstorms continue this morning along and north of US Highway 14 stretching southwest into southwestern SD with a mid level wave approaching and near the nose of the LLJ. Surface boundary is slowly moving south this morning, evident on radar around 3 AM CDT stretching from roughly Plankinton to Viborg to Milford. This boundary should continue to move to the south through the morning hours, later becoming a catalyst for thunderstorm development this afternoon and evening. Ahead of that though, expect these elevated showers and isolated storms to continue to move to the east this morning, with the greatest chances continuing to be around the US Hwy 14 corridor. Patchy areas of wildfire smoke may mix down to the surface through the day leading to locally reduced visibility and air quality. Moisture increases south of the boundary though the early afternoon hours, and with temperatures in this area into the upper 80s and lower 90s, should lead to a corridor of increased instability around or above 1500 J/kg (although the GFS/NAM are much greater in values) between the US Hwy 20 corridor and the I-90 corridor east of the James River Valley. Highest shear values (40+ kts) remain to the north of I-90 ergo offset from the best instability; however, shear values around 25 to 30 knots still support large hail and damaging wind gusts (especially with drier sub cloud layer). Tornado risk is very low; that said, should a storm be more surface based near the boundary, there may be enough 0-1 km shear to support a brief spin. The main threats with thunderstorms are hail up to the size of ping pong balls (1.5") and wind gusts to 70 mph between 2 and 10 PM. Locally heavy rainfall is possible. Storms should taper off late in the evening with the loss of instability. TONIGHT: There may be a lull in shower and thunderstorm activity before development commences along the elevated (850mb) front/WAA wing and near the nose of the LLJ around 1 AM. This activity looks to be more along and north of I-90, possibly as far north as US Hwy 14. Not much in the way of instability (less than 1000 J/kg) with mid level lapse rates less than 6.5 deg C/km. Stronger storms could produce hail to quarter size. Locally heavy rainfall is more of a concern tonight than during today, as storm motion and development will be nearly parallel to the west-east oriented front. Lower level winds continuing to shift to the south allow for efficient moisture transport, and a deep warm cloud layer over 10k ft supports efficient rainfall rates. Isolated to scattered flash flooding may occur, especially in urban or low lying areas. THURSDAY-THURSDAY NIGHT: Thursday's severe and heavy rain threats are going to be highly dependent on where boundaries end up after convection today through tonight. However, 11.00z guidance seems to be trending more northerly (toward US Hwy 14 or north) with the fronts and the mid level wave ejection, so trended the higher pops in that general direction. Less confident in the evolution of precipitation through the evening and into Thursday night with timing differences in frontal passages. Strong to severe storms are again possible, although confidence in timing and location is low. Hail to the size of ping pong balls and wind gusts to 70 mph would again be the main risks. Locally heavy rainfall is also possible, with more concern for areas which receive storms and heavy rainfall today and tonight. Areas north of I-90 and especially southwestern MN look to be at the greatest risk for heavier rainfall. Given the shift of the front north, raised highs a couple of degrees, especially south of I-90. Rainfall amounts into early Friday will be highly dependent on storm coverage; however, pockets of 2-4 inches are possible with about a 30% chance north and east of Sioux Falls. Mean values across the area are generally 0.25" to 1.25". FRIDAY-SATURDAY: Lingering showers and storms move east with the trough Friday. Mid and upper level ridging begins to build to the west with surface high pressure moving in as well. Could see some additional showers and isolated thunderstorms with a couple of ridge riding waves, but confidence is low on the details, especially with soundings showing a lack of moisture. Temperatures generally within 10 degrees of average. SUNDAY ONWARD: Ridging slides east and flattens into the early part of next week, with at least one more ridge rider Sunday. A more defined mid/upper level trough develops early next week, sliding east near the International Border sometime late weekend into early next week. Models are quite varied on the details of this trough and associated surface low, but this could bring additional shower and storm chances to the region. Guidance continues to diverge mid to late next week, with the 11.00z GFS most bullish on a deep mid/upper level trough moving through the Plains. Although details are uncertain, this pattern is conducive to periods of showers and thunderstorms. Machine learning and other guidance indicates that some strong to severe storm potential exists, so stay tuned to the forecast for updates - especially if you have outdoor or travel plans Sunday into next week. Temperatures stay in the mid 70s to upper 80s for highs and mid 50s to mid 60s for lows. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1250 PM CDT Wed Jun 11 2025 Mostly VFR conditions with occasional MVFR/IFR vsbys will be possible this TAF period mostly due to developing showers and thunderstorms. Taking a look across the area, all focus continues to be a line of developing showers and thunderstorms along a Wagner to Sioux Falls to Marshall, MN line. As this line continues to push eastwards, temporary MVFR vsbys along with a quick wind shift towards the northwest will be possible through about 21z. Otherwise, additional development along and south of I-90 overnight will lift northwards throughout the day on Thursday promoting MVFR to IFR ceilings and vsbys at times. Lastly, easterly winds will become more southeasterly winds to end the TAF period. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && DISCUSSION...SG AVIATION...05
Hazardous Weather Outlook National Weather Service Sioux Falls SD 445 AM CDT Wed Jun 11 2025 IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-NEZ013-014-SDZ038>040-050-052>071-120945- 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- 445 AM CDT Wed Jun 11 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. Wildfire smoke may cause surface impacts at times. Those sensitive to air pollutants should monitor air quality sources. Shower and thunderstorm chances increase this afternoon and this evening. A few storms could produce hail to ping pong ball size and wind gusts to 70 mph along and south of I-90. Locally heavy rainfall is possible. Additional showers and storms expected overnight with locally heavy rainfall. Hail to the size of quarters is possible. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. Periodic showers and thunderstorms continue into Friday. Storms Thursday afternoon and evening may be strong to severe with areas of heavy rainfall, though the location is more uncertain. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The Sioux Falls radar (KFSD), 48 km away, was scanning. The volume nearest the first event began at 18:23 UTC.
20 thunderstorm wind, 2 hail. Local standard time, as filed.
Thunderstorm winds blew down several trees in Rock Rapids.
Winds were measured by a personal weather station.
A roof was blown off a hog barn.
Winds were measured by a personal weather station.
A machine shed and empty grain bin were destroyed by thunderstorm winds, which also tipped over a semi-truck.
A cattle barn was significantly damaged by thunderstorm winds.
Several trees were downed by thunderstorm wind gusts.
Trees were reported down in Sibley from thunderstorm wind gusts.
Thunderstorm wind gusts removed the roof from a small shed.
Wind initially hit severe levels at 1300CST with a peak wind of 83 mph recorded at 1310CST at mesonet station RSYI4 near Sibley.
A lean-to was damaged by thunderstorm winds along State Highway 9.
Three-quarters of a mile of power poles were knocked down by thunderstorm wind gusts along 170th Street.
Winds were measured by a personal weather station.
Thunderstorms winds produced a considerable amount of blowing dust with severely reduced visibility.
Winds were measured by a personal weather station.
Pea sized hail accompanied 58 mph measured thunderstorm wind gusts.
Hail was mostly dime to nickel size, but some stones were as big as a quarter.
Tree damage from thunderstorm wind gusts occurred in the vicinity of 190th Avenue and 260th Street.
Two trees were blown down along 280th Street west of Fostoria.
Thunderstorm wind gusts removed a large tree limb.
Winds were measured by a personal weather station.
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, June 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: 1278311, 1278274, 1278305, 1278273, 1278315, 1278313, 1278278, 1278290, 1278308, 1278297, 1278312, 1278318, 1278293, 1278309, 1278310, 1278299, 1278271, 1278314, 1278307, 1278272, 1278301, 1278319.