A strong short-wave trough moved into the Northern Plains as a slow moving warm front lifted through North Dakota. Very strong instability developed by afternoon, along with increased deep layer shear.
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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 BIS wrote it up.
A strong short-wave trough moved into the Northern Plains as a slow moving warm front lifted through North Dakota. Very strong instability developed by afternoon, along with increased deep layer shear. The initial storms occurred over west-central and northwest North Dakota. The main concern with these storms was large hail and tornadoes. Multiple tornadoes occurred over western McKenzie County over a similar location, and one occurred in Williams County. Photos of the tornadoes submitted to the National Weather Service indicate that one of them in McKenzie County was quite large. With that said, no damage was reported given the tornadoes occurred in rugged terrain over a rural area, so all were rated EF-U, EF Unknown. As the evening went on, the threats shifted to a mix of strong winds, hail, and heavy rain. The city of Williston was hit the hardest with multiple storms passing over in a short period of time. Flash flooding occurred in the city, which floated vehicles and flooded basements. Hail to the size of tennis balls also fell, causing extensive home and vehicle damage. In addition, very strong winds were reported at the Williston airport, with gusts to 82 mph with one storm, then gusts to 93 mph with the next, causing roof damage. Later in the night the storms became more linear and grew towards the south, while the overall lines moved east. Wind became the primary concern as the storms moved towards the James River Valley where multiple wind damage events occurred. For the whole event, the largest hail reported was the size of tennis balls, in Williston in Williams County. The strongest reported wind gust was 93 mph at the Williston Airport, also in Williams County.
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 Bismarck, ND wrote its last area forecast discussion before the first event at Jun 10, 3:18 PM MST, 54 minutes earlier.
Area Forecast Discussion National Weather Service Bismarck ND 518 PM CDT Thu Jun 10 2021 .UPDATE... Issued at 517 PM CDT Thu Jun 10 2021 Tornado watch has now been expanded into far southwestern North Dakota. UPDATE Issued at 338 PM CDT Thu Jun 10 2021 Tornado watch has now been issued for much of northwest and portions of southwest North Dakota. Storms are starting to develop just to the west of the Montana border, and will continue to develop in earnest over the next hour or two. See below for details. && .SHORT TERM...(This evening through Friday) Issued at 217 PM CDT Thu Jun 10 2021 SYNOPSIS...A strong shortwave trough will eject off the Northern Rockies later today and develop negative tilt as it pivots into the Northern Plains by Friday morning. Surface low pressure over eastern Montana will intensify through the afternoon, with a well- defined wind shift and meridional low level convergence zone emerging. A warm/ stationary front will generally lie from near Williston to Bismarck into the southern Red River Valley. Strong diurnal heating and moisture return with upper 60s to lower 70s dewpoints in the warm sector will yield extreme instability around of 3,000-5,000 J/kg SBCAPE. Veering wind profiles and increasing speeds aloft will result in increasing shear, both temporally and vertically from the surface. These conditions will set the stage for an outbreak of severe thunderstorms across western and central North Dakota late this afternoon through tonight. SHORT TERM...High-impact weather is expected for the short term period. The biggest concern is for severe thunderstorms later this afternoon through tonight. Other hazards include heat in south central and southeast North Dakota through the early evening, strong southeasterly winds in northwest and west central North Dakota this afternoon, windy conditions everywhere on Friday, and near critical fire weather conditions in southwest North Dakota Friday afternoon. A Heat Advisory remains in effect for portions of south central and southeast North Dakota this afternoon. Expect late afternoon highs in the mid to upper 90s combining with mid 60s dewpoints to produce heat indices around 100. A Wind Advisory is in effect for parts of northwest and west central North Dakota this afternoon. Sustained winds in the 30 to 40 mph range have routinely been observed in these areas. There are 3 main areas of focus for convective initiation, which will be discussed in order of increasing probability and severity. There is a non-zero chance that isolated storms could develop along the warm front from central into southeast North Dakota during the mid to late afternoon. CIN is forecast to be weaker along the front, but deep layer forcing will essentially be absent. If a storm does develop in this area during the afternoon, large hail would be the primary threat in a high CAPE/moderate to low shear environment. This potential appears to be the least likely and least concerning at this time. Convective initiation is more likely to occur along the meridional low level convergence zone near the ND/MT border later this afternoon. There are some concerns about mid level capping, but with mid level height falls, strong low level frontogenesis, and strong boundary layer mixing all present, think that CIN will work more to limit the coverage of convection rather than suppress it completely. Storm mode should initially be discrete supercells, with hodographs suggesting splits with right-movers being dominant. Very large hail and damaging wind gusts are likely with any supercell that develops. There is also a threat for tornadoes, especially in closer proximity to the intersection of the lee trough and warm front in northwest North Dakota where low level shear and helicity have already reached values that are favorable for tornadogenesis. Outflow boundary interactions could also produce localized instances of an increased tornado threat. There is some uncertainty on the evolution of these storms, particularly if and how quickly upscale growth can occur. Strong low level forcing and storm motion around a 45 degree angle to the lee trough would favor a quicker upscale growth, but potential storm motion into a relatively less unstable air mass near the international border and the presence of CIN could prolong a discrete mode. If this convection congeals into a linear mode, damaging wind would become the dominant threat. The strongest forcing aloft is expected to arrive in western North Dakota this evening. This will likely result in a widespread expansion of ongoing convection or robust convective development if none is present at that time. One or two strong linear complexes with embedded mesocyclones will likely sweep across the state this evening through tonight, with 3,000 J/kg MUCAPE, 1,000 J/kg DCAPE, and increasing effective bulk shear supporting a widespread and potentially significant damaging wind threat. Around 100-200 m2/s2 helicity and 20-30 kts shear in the 0-500 m layer could also promote a QLCS tornado threat. Once these lines mature, they will likely race across the state through the overnight. Heavy rain is possible with any storm given 1-2 inch PWAT and deep layer warm cloud processes. However, we are not expecting a widespread flash flooding concern due to the fast moving nature of the nocturnal convection, and the more widely scattered coverage of convection prior to sunset. The exception would be over areas that received excessive rainfall earlier this week. We will also have to watch for training convection or multiple rounds of heavy rain at similar locations, but these potentials seem more localized and have a low probability. On Friday, the surface low is forecast to pivot into southern Canada. Wrap-around showers and embedded non-severe thunderstorms are possible mainly across the northern half of the state Friday morning into the afternoon. The presence of the stronger pressure gradient will bring westerly winds around sustained speeds of 25-30 mph, with gusts near 45 mph. A Wind Advisory may be needed, but that will be considered after the severe storm threat has ended. Additionally, a dry air mass being advected into the region combined with the winds will likely result in near critical fire weather conditions Friday afternoon, although fuels have become considerably unfavorable for fire concerns. It will be noticeably cooler on Friday, but highs are still forecast to be within 5 degrees of normal values. .LONG TERM...(Friday night through Thursday) Issued at 217 PM CDT Thu Jun 10 2021 Deep layer ridging is favored to build over the central CONUS this weekend into next week, returning temperatures to well above normal and keeping thunderstorm chances out of the forecast for the time being. A few chances for thunderstorms may emerge in later forecast updates, but predictability is far too low to include any at this time. && .AVIATION...(For the 18Z TAFS through 18Z Friday afternoon) Issued at 105 PM CDT Thu Jun 10 2021 Severe thunderstorms are expected across western and central North Dakota later this afternoon through tonight. +50 kt gusts are possible with any storm, especially at KBIS and KMOT. The greatest potential for large hail is at KXWA, but hail cannot be ruled out at other terminals. Expect MVFR ceilings and IFR to LIFR visibility with thunderstorms. Prevailing MVFR ceilings are possible across northern North Dakota late tonight into Friday morning. Prevailing easterly winds ahead of thunderstorms will become westerly behind the storms. && .BIS WATCHES/WARNINGS/ADVISORIES... Wind Advisory until 6 PM CDT /5 PM MDT/ this evening for NDZ001- 009-010-017-031-032. Heat Advisory until 8 PM CDT this evening for NDZ046>048-050-051. && UPDATE...JJS SHORT TERM...Hollan LONG TERM...Hollan AVIATION...Hollan
Hazardous Weather Outlook National Weather Service Bismarck ND 605 PM CDT Thu Jun 10 2021 NDZ001-002-009-010-017-018-031>033-040-041-043-044-112315- Divide-Burke-Williams-Mountrail-McKenzie-Dunn-Golden Valley- Billings-Stark-Slope-Hettinger-Bowman-Adams- 605 PM CDT Thu Jun 10 2021 /505 PM MDT Thu Jun 10 2021/ This Hazardous Weather Outlook is for portions of northwest North Dakota and southwest North Dakota. .DAY ONE...Tonight Severe thunderstorms are expected into tonight. Very large hail up to softball size, damaging wind gusts to at least 80 mph, tornadoes, and heavy rain are possible. The greatest threat for large hail and tornadoes is in northwest into portions of southwest North Dakota. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Gusty westerly winds are forecast on Friday. Combined with low humidity, near critical fire weather conditions are expected. Near critical fire weather conditions will be possible this weekend through the middle portions of next week. .SPOTTER INFORMATION STATEMENT... Spotter are encouraged to contact the National Weather Service with any severe weather reports. NDZ003>005-011>013-019>023-025-034>037-042-045-112315- Renville-Bottineau-Rolette-Ward-McHenry-Pierce-Mercer-Oliver- McLean-Sheridan-Wells-Foster-Morton-Burleigh-Kidder-Stutsman- Grant-Sioux- 605 PM CDT Thu Jun 10 2021 /505 PM MDT Thu Jun 10 2021/ This Hazardous Weather Outlook is for portions of north central North Dakota, south central North Dakota, and southeast North Dakota. .DAY ONE...Tonight Severe thunderstorms are expected later this afternoon through tonight. Very large hail up to tennis ball size, damaging wind gusts to at least 80 mph, isolated tornadoes, and heavy rain are possible. The greatest threat for large hail and tornadoes is in northwest and parts of southwest North Dakota. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Gusty westerly winds are forecast on Friday. Combined with low humidity, near critical fire weather conditions are expected. Near critical fire weather conditions will be possible this weekend through the middle portions of next week. .SPOTTER INFORMATION STATEMENT... Spotter are encouraged to contact the National Weather Service with any severe weather reports. NDZ046>048-050-051-112315- Emmons-Logan-La Moure-McIntosh-Dickey- 605 PM CDT Thu Jun 10 2021 This Hazardous Weather Outlook is for portions of south central North Dakota and southeast North Dakota. .DAY ONE...Tonight A Heat Advisory is in effect this afternoon and early evening. See weather.gov/bis for additional information. Severe thunderstorms are expected later this evening through tonight. Large hail up to ping pong ball size, damaging wind gusts to at least 80 mph, a few tornadoes, and very heavy rain are possible. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Near critical fire weather conditions will be possible this weekend through the middle portions of next week. .SPOTTER INFORMATION STATEMENT... Spotter are encouraged to contact the National Weather Service with any severe weather reports.
The Glasgow radar (KGGW), 216 km away, was scanning. The volume nearest the first event began at 23:12 UTC.
44 thunderstorm wind, 17 hail, 4 tornado, 1 flash flood. Local standard time, as filed.
The tornado touched down in an open field northeast of Skaar. There was no damage to evaluate and so by National Weather Service policy the tornado is rated EF Unknown.
The tornado touched down in an open field southwest of Sather Dam. There was no damage to evaluate and so by National Weather Service policy the tornado is rated EF Unknown.
The tornado touched down and moved through open rangeland in rugged terrain southwest of Sather Dam, near the location of the previous tornado report. This tornado was noted to be quite large, and long lasting. There was no damage to evaluate and so by National Weather Service policy the tornado is rated EF Unknown.
Part of a roof was blown off a building, and another small building was blown over.
This was the first of multiple rounds of hail to strike the Williston area the evening of June 10. With this round, hail up to the size of tennis balls fell over the Williston area. This caused damage to many roofs and vehicles, including damaging every police car in the city, and every vehicle parked in the Williams County facility lot. In addition, strong winds with this storm blew a roof off a truck and car wash.
A roof was damaged.
The tornado touched down in an open field east of Williston. There was no damage to evaluate and so by National Weather Service policy the tornado is rated EF Unknown.
Up to five inches of rain fell in the Williston area as multiple rounds of thunderstorms passed through. This led to widespread street flooding, with water affecting many homes. In addition, multiple vehicles were damaged by the flood waters. This includes a combination of parked vehicles and ones where the driver entered the flood waters.
A large pole barn was heavily damaged with one end of the building and an adjacent part of the roof destroyed.
This is the second in a series of storms to strike the Williston area. Ping pong size hail accompanied this storm, along with very heavy rainfall. Additional damage was done to roofs and vehicles.
Mountrail-Williams electric recorded 52 poles broken, which includes a one-mile long stretch where every pole was broken southeast of Grenora. In addition, a large tree was blown down in Zahl.
The public estimated wind gusts to 60 mph.
Three inch tree limbs were broken, and some power poles were broken.
Trees were damaged.
A tree was down in town, along with a power line.
One inch diameter tree limbs were broken. Some shingles blew off a structure.
Three inch diameter tree limbs were broken, and some power poles were broken.
Damage occurred in and around the city of Glen Ullin. About a mile west of town, outbuildings were severely damaged, and a roof on an industrial building was damaged. In town, A five inch diameter tree was broken over.
Tree damage occurred.
A recreational vehicle was tipped over, and a small garage was shifted off its foundation.
A chicken coop was destroyed.
Six inch diameter branches from a one-hundred year old tree were broken down.
A hopper-style grain bin blew over.
A pole barn building was blown down.
Large trees were blown down.
A trained spotter estimated thunderstorm wind gusts of 60 mph.
A street light was bent at the base.
A camper was blown onto its side, and a pontoon boat on a lift was rolled over, with the dock damaged.
Tree branches several inches wide punctured a house roof.
Several large tree branches around Oakes were snapped. Garaged doors were blown in, and a home TV tower was bent over.
A 40 foot tall evergreen was uprooted and fell onto a shed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in North Dakota in 2021Every state in 2021This day in weather historyThe tornado archive for North Dakota, 2021Warnings in North Dakota, 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: 964497, 962335, 964498, 962348, 962351, 964759, 962354, 962349, 962350, 962355, 962353, 962357, 962358, 962359, 962362, 962360, 962356, 962363, 964760, 964562, 962365, 964452, 964458, 964460, 964464, 962364, 964466, 964467, 964468, 964469, 964470, 964471, 964453, 964454, 964455, 964456, 964459, 964461, 964462, 964463, and more.