A few thunderstorms developed during the late morning hours over central North Dakota where southerly low level flow increased instability, and deep layer shear was elevated. Initially, a nearly stationary supercell developed over Oliver County.
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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 few thunderstorms developed during the late morning hours over central North Dakota where southerly low level flow increased instability, and deep layer shear was elevated. Initially, a nearly stationary supercell developed over Oliver County. The storm produced large hail and damaging wind gusts, along with torrential rain that led to flash flooding and damaging gravel roads. The storm eventually started moving to the south-southeast, continuing to produce severe weather in its path. Substantial damage occurred in Morton County north and east of the city of Flasher where hail up to the size of baseballs and wind gusts estimated to 80 mph severely damaged homes and vehicles, and overturned a semi-truck. Additional storms developed in the area. One intense supercell thunderstorm moved through Hettinger and Adams counties producing three inch diameter hail that destroyed crops and greatly damaged buildings and vehicles.
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 Aug 30, 8:09 AM CST, 1 hour 51 minutes earlier.
Area Forecast Discussion National Weather Service Bismarck ND 909 AM CDT Mon Aug 30 2021 .UPDATE... Issued at 853 AM CDT Mon Aug 30 2021 No major changes for this update. Only blended in latest observations and made slight adjustments to sky cover based on satellite trends. CAMs continue to indicate the potential for thunderstorms initiating as early as late morning or early afternoon. Still not entirely confident in this solution. However, should anything develop that early, will likely be elevated in nature initially. UPDATE Issued at 617 AM CDT Mon Aug 30 2021 No major changes were needed for this update. Just blended in the latest observations of the sensible weather fields into the going forecast. && .SHORT TERM...(Today and tonight) Issued at 412 AM CDT Mon Aug 30 2021 The potential for severe thunderstorms this afternoon and evening across the west central and southwest highlights the short term forecast period. Early this morning, nearly zonal flow was noted at the mid to upper levels, with a hint of subtle ridging near the Montana border. A weak shortwave was also noted on water vapor satellite imagery embedded within the flow over central Montana. This wave should be the trigger to initiate a few isolated thunderstorms across western and central North Dakota this afternoon and evening. Warm air advection and moisture will be on the increase through the day, leading to a slightly warmer day than yesterday with highs in the mid 70s across the northeast to the mid 80s southwest. Dewpoints across much of the central and south will rise into the mid 50s to lower 60s (highest values southwest and south central). These temperature/moisture profiles will lead to plenty of destabilization across the west central and southwest this afternoon, leading to MLCAPE values in the 1500 to 2500 J/kg range. This area of enhanced buoyancy will be collocated with deep layer shear values on the order of 35 to 45 knots, which would certainly be sufficient for supercells. While the parameter space will be favorable for very large hail up to two inches in diameter and winds gusts to 70 mph, there remains a lack of an obvious trigger. The one exception will be the aforementioned weak wave that will move through aloft (bringing with it modest height falls and cooler temperatures aloft, leading to steep mid level lapse rates southwest). Thus, the severe threat will be conditional based on initiation, but it seems likely that at least a handful of storms will form. Most CAMs have been consistent with initiating isolated storms over the west and south central during the 20z to 22z time frame. These initial supercells should stay fairly discrete given the isolated nature of the convection, but the severe threat may last into the evening as a modest low level jet kicks in and storms try to grow upscale south central. Most of the activity should slide off into north central South Dakota around and after 06z Tuesday. Expect overnight lows in the 50s. .LONG TERM...(Tuesday through Sunday) Issued at 412 AM CDT Mon Aug 30 2021 An upper level ridge axis amplifies on Tuesday overhead as a Pacific Northwest trough digs south and east. This will keep most of the day dry on Tuesday with only a few clouds hovering around. Tuesday afternoon will also feature a stiff breeze out of the southeast with sustained winds up to 25 mph and gusts to 35 mph. A shortwave will then eject from the western trough as ridging moves east, skirting the northwest and north central overnight. This will lead to chances of showers and storms mainly across the north through Wednesday morning. The stronger wave then comes through later on Wednesday, which should bring widespread showers and thunderstorms to western and central North Dakota. The forecast CAPE/shear overlap would favor a chance for severe storms across most of the central and into the Turtle Mountains and James River Valley. Specific details regarding exact location and timing remain uncertain, but this is a period we continue to watch closely. A few more thunderstorms will be possible on Thursday as the base of the trough moves overhead by the night time hours. While buoyancy will be modest, shear will be strong so a few stronger updrafts are not out of the question. Showers (and perhaps a storm or two) embedded in cyclonic flow will then be possible Friday through Saturday morning behind the trough. Temperatures will remain around or slightly below normal for this time of year through the extended. && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 617 AM CDT Mon Aug 30 2021 VFR conditions are expected through the period. Isolated thunderstorms are possible this afternoon and evening across portions of the west and central. Across the southwest, a few storms could become strong to severe with very large hail up to two inches in diameter and wind gusts to 70 mph. Due to the isolated nature of these storms and uncertainty regarding exact location and timing, have kept mention of any kind of precipitation out of the TAF forecast for now. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && UPDATE...Telken SHORT TERM...ZH LONG TERM...ZH AVIATION...ZH
Hazardous Weather Outlook National Weather Service Bismarck ND 842 AM CDT Mon Aug 30 2021 NDZ001>005-009-025-037-311345- Divide-Burke-Renville-Bottineau-Rolette-Williams-Foster-Stutsman- 842 AM CDT Mon Aug 30 2021 This Hazardous Weather Outlook is for portions of north central North Dakota, northwest North Dakota, and southeast North Dakota. .DAY ONE...Today and Tonight The probability for widespread hazardous weather is low. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday There is a chance of thunderstorms on Wednesday afternoon and evening across much of western and central North Dakota. A few of these storms could become strong to severe. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed. NDZ017>021-031>035-040>046-311345- McKenzie-Dunn-Mercer-Oliver-McLean-Golden Valley-Billings-Stark- Morton-Burleigh-Slope-Hettinger-Grant-Bowman-Adams-Sioux-Emmons- 842 AM CDT Mon Aug 30 2021 /742 AM MDT Mon Aug 30 2021/ This Hazardous Weather Outlook is for portions of northwest North Dakota, south central North Dakota, and southwest North Dakota. .DAY ONE...Today and Tonight There is a slight chance for thunderstorms this afternoon and evening. A storm or two could become severe. The main threats would be hail to two inches in diameter and wind gusts to 70 mph. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday There is a chance of thunderstorms on Wednesday afternoon and evening across much of western and central North Dakota. A few of these storms could become strong to severe. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed. NDZ010>013-022-023-036-047-048-050-051-311345- Mountrail-Ward-McHenry-Pierce-Sheridan-Wells-Kidder-Logan- La Moure-McIntosh-Dickey- 842 AM CDT Mon Aug 30 2021 This Hazardous Weather Outlook is for portions of north central North Dakota, northwest North Dakota, south central North Dakota, and southeast North Dakota. .DAY ONE...Today and Tonight There is a slight chance for thunderstorms this afternoon and evening. While severe weather is not anticipated, a few storms could become strong with small hail and gusty winds. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday There is a chance of thunderstorms on Wednesday afternoon and evening across much of western and central North Dakota. A few of these storms could become strong to severe. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed. Telken
Special Weather Statement National Weather Service Bismarck ND 1051 AM CDT Mon Aug 30 2021 NDZ020-301615- Oliver ND- 1051 AM CDT Mon Aug 30 2021 ...A strong thunderstorm will impact portions of southwestern Oliver County through 1115 AM CDT... At 1050 AM CDT, Doppler radar was tracking a strong thunderstorm 9 miles southeast of Beulah, moving southeast at 15 mph. HAZARD...Nickel size hail. SOURCE...Radar indicated. IMPACT...Minor damage to outdoor objects is possible. This storm will remain over mainly rural areas of western Oliver County. PRECAUTIONARY/PREPAREDNESS ACTIONS... If outdoors, consider seeking shelter inside a building. Torrential rainfall is also occurring with this storm and may lead to localized flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 4713 10177 4724 10169 4719 10139 4700 10157 TIME...MOT...LOC 1550Z 296DEG 12KT 4715 10165 MAX HAIL SIZE...0.88 IN MAX WIND GUST...<30 MPH SCHILD
The Bismarck radar (KBIS), 85 km away, was scanning. The volume nearest the first event began at 16:00 UTC.
20 hail, 2 thunderstorm wind, 1 flash flood. Local standard time, as filed.
An unattached porch was tipped over.
Over four inches of rain falling from a slow moving thunderstorm led to flash flooding. Rural roads had water flowing over them, washing gravel away and making them impassable.
A pickup truck was damaged.
Multiple homes in the area were heavily damaged, which included broken windows and destroyed siding. In addition, a few campers were also damaged.
Multiple vehicles were damaged. A canola crop was severely damaged.
A soybean crop was destroyed.
A semi-truck and trailer were blown over by thunderstorm winds. The very strong winds continued for a few minutes after the truck blew over.
Vehicles were severely damaged, which included broken windshields.
Very large hail combined with wind gusts to cause extensive damage. At one farmstead, all windows were broken out of the north side of two homes. Steel siding was dented on one home, and vinyl siding was destroyed on the other. Five vehicles had their windows broken. Crops were flattened and trees were stripped of leaves. Other farmsteads in the area also had broken windows in their homes, and destroyed crops.
A long lived supercell thunderstorm produced a path of destruction near Haynes. At one farm, large hail punched many holes through the metal roofs on pole barns and also into a hot-tub cover. Five vehicles were substantially damaged. Windows were broken on pole barns, and an exhaust vent for a pole barn furnace was busted off. To the south-southeast the destruction continued, with very large hail continuing to fall. In addition, strong thunderstorm winds accompanied the hail, shredding a field of lush eight foot tall corn, which was considered some of the nicest in the county, down to knee high.
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 historyWarnings in North Dakota, August 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: 978022, 977779, 978029, 977780, 977782, 977783, 977784, 977785, 977788, 977791, 977793, 977797, 977798, 977789, 977820, 977795, 978023, 978024, 978027, 977819, 978026, 978028, 978025.