Severe storms which developed across western South Dakota during the evening of June 10 translated eastward through the overnight hours. An increasing low-level jet enhanced shear, with an environment strongly supportive of developing outflow pools with DCAPE of 1500-2000 J/kg.
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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.
Severe storms which developed across western South Dakota during the evening of June 10 translated eastward through the overnight hours. An increasing low-level jet enhanced shear, with an environment strongly supportive of developing outflow pools with DCAPE of 1500-2000 J/kg. Storms congealed into a linear bowing structure through the late overnight and early morning hours, producing strong to damaging wind gusts as storms moved into 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 Jun 11, 3:02 AM CST, 2 hours 36 minutes earlier.
AREA FORECAST DISCUSSION National Weather Service Sioux Falls SD 402 AM CDT Fri Jun 11 2021 .SHORT TERM...(Today through Saturday afternoon) Issued at 352 AM CDT Fri Jun 11 2021 Line of strong to isolated severe storms currently over our far western forecast area. This line still expected to advance east through the morning, gradually weakening as it progresses into less unstable air mass. Will continue to see potential for isolated stronger gusts within the line, with greater threat generally focused west of the I-29 corridor as low level shear likewise weakens farther to the east. Slowest of models hold some lingering trailing showers in our far southeast counties into the early afternoon, with skies quickly clearing behind the precip through the day. Much drier air mass filters into the forecast area, along with cooler temperatures, but given potential for deeper mixing in northwest post-frontal flow, have still hedged toward the warmer side of guidance for highs most areas. This generally yields highs in the 80s, or a good 10-15F cooler than yesterday, though still at/above normal for this time of year. Lower humidity levels along with decreasing winds and clear skies tonight should allow for a comfortable night with lows in the 50s, possibly worthy of opening some windows for those able to do so! Surface ridge axis moves across the forecast area on Saturday, keeping skies clear and winds on the light side. Warmer low level air does begin to nudge back into the area, so highs will favor the higher end of the 80s. .LONG TERM...(Saturday night through Thursday) Issued at 352 AM CDT Fri Jun 11 2021 After a short but welcome reprieve, hot and dry will again become the dominant theme of the upcoming week. Upper ridge builds once again over the Rockies/western Plains through the first half of the week, with ensemble mean 500mb height anomalies as much as 210-230m above normal in southern Saskatchewan Monday-Tuesday. This position of the ridge axis just to our west, placing us in a northwest flow regime early next week, leaving the door open for weak ripples to slide southeast across the region. Any of these weak waves could trigger spotty rainfall chances, but low level flow pattern is not conducive to deep moisture flowing north from the Gulf, so do not foresee any substantial rains which could provide relief from our expanding drought conditions through at least the next week. As far as temperatures, heat begins to build back in by Sunday, with 850mb readings topping 20C. Weak back door "cool" front begins to push southwest across the forecast area late Monday, with ensemble mean 850mb temperature anomalies showing potential for near seasonal air to approach our eastern counties on Tuesday. Some uncertainty in how far west the cooler air advances, so there is potential that our highs could be more widespread 80s if cooler solutions pan out. But for now enough support to keep at least lower 90s across our western and southern areas, with 80s more likely east of KBKX-KSPW line. By Wednesday, stronger wave is projected to push into the Canadian Rockies, suppressing the dominant ridge axis into the northern CONUS as the wave continues east into the Canadian Prairies. The thermal ridge likewise transitions to a more west-east orientation over our forecast area Thursday, as a cold front trailing from the Canadian wave pushes into the northern Plains. This should result in Thursday being the warmest day of the week, followed by a more seasonable day again Friday, but seeing typical timing differences among the models at this range, with some ensemble members holding on to the warmer air at least another 24 hours. Could see scattered showers/storms with the front late next week, but again, timing uncertainty will preclude adding pops in at this point. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1027 PM CDT Thu Jun 10 2021 A line of thunderstorms is expected to move into central SD by 07Z, then track into the the KHON vicinity around 09Z, and KFSD and KSUX around 11-12Z. These storms may have damaging winds in excess of 40 kts as they move through. Showers and storms will push out of the area by late morning on Friday. Winds will transition from southerly to northwesterly by Friday morning, gusting 20 to 25 kts through the afternoon. Winds will diminish on Friday evening. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && SHORT TERM...JH LONG TERM...JH AVIATION...JM
Hazardous Weather Outlook National Weather Service Sioux Falls SD 432 AM CDT Fri Jun 11 2021 SDZ038-039-050-052>055-057>061-063>065-068-120945- Beadle-Kingsbury-Gregory-Jerauld-Sanborn-Miner-Lake-Brule-Aurora- Davison-Hanson-McCook-Charles Mix-Douglas-Hutchinson-Bon Homme- 432 AM CDT Fri Jun 11 2021 This Hazardous Weather Outlook is for central South Dakota, east central South Dakota, south central South Dakota and southeast South Dakota. .DAY ONE...Today and tonight. A line of thunderstorms will push east of the area early this morning. After the storms exit, no hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Saturday through Thursday. Heat will build back into the region through the weekend, with afternoon temperatures and heat indices in the 90s returning from Sunday through much of next week. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-SDZ040-056-062-067-120945- Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee- Buena Vista-Woodbury-Ida-Lincoln-Murray-Cottonwood-Nobles-Jackson- Pipestone-Rock-Brookings-Moody-Minnehaha- 432 AM CDT Fri Jun 11 2021 This Hazardous Weather Outlook is for northwest Iowa, west central Iowa, southwest Minnesota, east central South Dakota and southeast South Dakota. .DAY ONE...Today and tonight. An area of showers and thunderstorms will move across the region this morning. Severe weather is not expected, but gusty winds are possible as the storms move through. .DAYS TWO THROUGH SEVEN...Saturday through Thursday. Heat will build back into the region through the weekend, with afternoon temperatures and heat indices in the 90s returning from Sunday through much of next week. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. NEZ013-014-SDZ066-069>071-120945- Dixon-Dakota-Turner-Yankton-Clay-Union- 432 AM CDT Fri Jun 11 2021 This Hazardous Weather Outlook is for northeast Nebraska and southeast South Dakota. .DAY ONE...Today and tonight. An area of showers and thunderstorms will move across the region this morning. Isolated stronger wind gusts are possible with any storms early this morning. .DAYS TWO THROUGH SEVEN...Saturday through Thursday. Heat will build back into the region through the weekend, with afternoon temperatures and heat indices in the 90s returning from Sunday through much of next week. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
327 AM CDT FRI JUN 11 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0315 AM TSTM WND GST 3 S CHAMBERLAIN 43.77N 99.32W
06/11/2021 M62 MPH BRULE SD ASOS
&&
AKPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
458 AM CDT FRI JUN 11 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0453 AM TSTM WND GST 3 N MITCHELL 43.77N 98.04W
06/11/2021 M62 MPH DAVISON SD ASOS
&&
AKPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
531 AM CDT FRI JUN 11 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0510 AM TSTM WND GST 5 S CANOVA 43.81N 97.49W
06/11/2021 M55 MPH MCCOOK SD MESONET
TIME ESTIMATED VIA RADAR.
&&
AKPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
626 AM CDT FRI JUN 11 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0556 AM TSTM WND GST 2 NE YANKTON 42.92N 97.37W
06/11/2021 M56 MPH YANKTON SD AWOS
&&
AKThe Sioux Falls radar (KFSD), 85 km away, was scanning. The volume nearest the first event began at 11:40 UTC.
1 thunderstorm wind. Local standard time, as filed.
Thunderstorm winds destroyed a 100 by 180 foot machine shed. Property damage costs are a rough estimate.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2021Every state in 2021This day in weather historyWarnings in Iowa, June 2021
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: 966050.