A negatively tilted trough and associated cold front pushed across the CWA on the morning of June 11th. Severe thunderstorms developed along the pre-frontal trough, as well as the cold front.
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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 FGF wrote it up.
A negatively tilted trough and associated cold front pushed across the CWA on the morning of June 11th. Severe thunderstorms developed along the pre-frontal trough, as well as the cold front. Numerous wind damage, and hail reports were submitted, as well as a tornado.
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 Grand Forks, ND wrote its last area forecast discussion before the first event at Jun 11, 2:05 AM CST, 44 minutes earlier.
Area Forecast Discussion National Weather Service Grand Forks ND 305 AM CDT Fri Jun 11 2021 .SHORT TERM...(Today through Saturday) Issued at 305 AM CDT Fri Jun 11 2021 The main forecast challenge is the severe weather potential early this morning. A severe thunderstorms watch has already been issued for eastern North Dakota and some adjacent counties of northwest and west central Minnesota until 7 am. As of about 3 am, surface low pressure was located somewhere between Bismarck and Minot, with a warm front extending out to the east-southeast from it, to somewhere over southeast North Dakota. Temperatures were still very mild, with 86 degrees still being reported at both Aberdeen SD and Gwinner ND. Fargo was reporting a dewpoint of 70, as was Detroit Lakes MN. The SPC mesoanalysis page showed a nice low level jet punching up through the central Dakotas, but the best 0-6km bulk shear lags behind the line of storms from east of Minot to east of Bismarck. These storms have a history of producing some damaging wind gusts, but overall they have mainly been below 50 knots. The main question is what happens as these storms move into eastern North Dakota. There was a trend yesterday evening with more of the high resolution models showing the current storms continuing to move east, but the stronger storms diving more into South Dakota. The latest HRRR shows the line of storms moving into the Red River Valley by sunrise, but nothing too exciting. The HREF from 12z yesterday showed the 4hr neighborhood probability of severe wind moving toward eastern ND and basically dropping off to nothing. The SPC 3hr calibrated severe thunderstorm graphic shows the best values through 12z dropping toward the ND/SD border, then dropping off to nothing thereafter. This is the reason the severe thunderstorm watch goes until 12z. The line of storms looks to weaken pretty quickly after 12z as the storms cross the Red River, and they may die off sometime later this morning. The rest of the day will feature increasing west winds and much cooler temperatures. Quiet weather tonight into Saturday as well. .LONG TERM...(Saturday night through Thursday) Issued at 305 AM CDT Fri Jun 11 2021 An amplifying upper ridge on Sunday will keep impacts to the minimum during the long term period. The best opportunity for summer impacts could be Wednesday with hot temperatures, but at the current time strong mixing from southerly winds will keep RH values low and heat indices in check. Zonal flow at the beginning of the long term period quickly amplifies with an upper ridge extending from AZ into Alb/Sask, with upper lows off the Pacific NW coast and over the Hudson Bay. The ridging will be in place for the first half of the work week, with highs in the 80s and 90s. The high temperatures peak Wednesday with eastern North Dakota reaching the mid to upper 90s. Gusty south winds will result in mixing sufficient to keep RH values in the 20s and heat advisory potential minimal. NAEFS climatological percentiles are maxed out over western and central ND, giving me good confidence in a hot summer day. The Pacific upper low moves into Manitoba by Thursday, increasing chances for precipitation Thursday afternoon. Slightly cooler air will follow the late week system with Day 7 temperatures looking to be in the 70s and 80s. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1139 PM CDT Thu Jun 10 2021 Aviation concern still focused on eventual arrival of thunderstorm activity during the first 6hr of the TAF period. Strong to severe storms will be possible once this arrives in eastern ND with showers/weaker thunder favored in MN. Arrival right now looks to be first at KDVL by 09Z and closer to 12Z at KGFK/KFAR. Eventually prevailing dry conditions should return Friday, though it could be delayed if there is redevelopment of showers/storms during the daytime period (hard to say at this point). IFR or lower conditions will be possible with stronger thunderstorm activity. Southwest to west winds increase behind the cold front during the day Friday and gusts in excess of 30kt appear likely in eastern ND (strongest at KDVL). These should decrease with sunset, though gusty winds may linger a KDVL into Friday night. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. SHORT TERM...Godon LONG TERM...Speicher AVIATION...DJR
Hazardous Weather Outlook National Weather Service Grand Forks ND 314 AM CDT Fri Jun 11 2021 MNZ001>003-029-NDZ006>008-014>016-024-026>030-038-039-049-052>054- 120815- West Polk-Norman-Clay-Wilkin-Towner-Cavalier-Pembina-Benson- Ramsey-Eastern Walsh-Eddy-Nelson-Grand Forks-Griggs-Steele-Traill- Barnes-Cass-Ransom-Sargent-Richland-Western Walsh- 314 AM CDT Fri Jun 11 2021 This hazardous weather outlook is for portions of eastern North Dakota, west central and northwest Minnesota. .DAY ONE...Today and Tonight Scattered thunderstorms are possible through the early morning hours. Some of these storms may be severe with damaging wind gusts up to 75 mph and 1 inch diameter hail. .DAYS TWO THROUGH SEVEN...Saturday through Thursday The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to contact the National Weather Service with any severe weather reports. MNZ004>009-013>017-022>024-027-028-030>032-040-120815- Kittson-Roseau-Lake Of The Woods-West Marshall-East Marshall- North Beltrami-Pennington-Red Lake-East Polk-North Clearwater- South Beltrami-Mahnomen-South Clearwater-Hubbard-West Becker- East Becker-West Otter Tail-East Otter Tail-Wadena-Grant- 314 AM CDT Fri Jun 11 2021 This hazardous weather outlook is for portions of west central and northwest Minnesota. .DAY ONE...Today and Tonight Scattered thunderstorms are possible east of the Red River around or after 6 am. The probability for widespread hazardous weather is low. .DAYS TWO THROUGH SEVEN...Saturday through Thursday The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
Special Weather Statement
National Weather Service Grand Forks ND
336 AM CDT Fri Jun 11 2021
NDZ028-029-038-039-110930-
Griggs ND-Steele ND-Barnes ND-Cass ND-
336 AM CDT Fri Jun 11 2021
...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN CASS...GRIGGS...
BARNES AND STEELE COUNTIES UNTIL 430 AM CDT...
At 336 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 6 miles southwest of Juanita to near Ypsilanti.
Movement was east at 55 mph.
Wind gusts of 50 to 55 mph will be possible with these storms.
Locations impacted include...
Valley City, Cooperstown, Golden Lake, Finley, Hope, Tower City and
Page.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.
To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
office in Grand Forks.
&&
A Severe Thunderstorm Watch remains in effect until 700 AM CDT for
southeastern North Dakota.
LAT...LON 4754 9850 4767 9761 4689 9731 4676 9844
4698 9844 4698 9847 4732 9847 4733 9850
TIME...MOT...LOC 0836Z 255DEG 49KT 4743 9877 4676 9853
LynchThe Fargo/Grand Forks radar (KMVX), 94 km away, was scanning. The volume nearest the first event began at 08:51 UTC.
34 thunderstorm wind, 3 hail. Local standard time, as filed.
Large, empty grain bins at an elevator complex were caved in and collapsed. Peak winds estimated to be 80 mph, with multiple long duration gusts.
Wind gust of 58 mph reported via NDAWN.
Peak wind was measured at an NDAWN station.
Peak wind was measured at a North Dakota DOT RWIS station.
Peak wind report at 10 meters via NDAWN.
Peak gust of 65 mph reported via NDAWN.
Peak wind measured at the Cooperstown Airport KS32.
Peak wind measured at a personal weather station.
Peak gust of 81 mph reported at the Cooperstown Airport AWOS.
Peak wind was measured at an NDAWN station at 10 meters.
Wind gust of 83 mph was measured at a personal weather station.
Wind gust of 59 mph was reported via NDAWN.
Wind gust of 72 mph was reported by the NDAWN in Lisbon.
Hail report was relayed via media.
Peak wind gust was measured at the Gwinner Airport KGWR.
Peak wind gust measured via NDAWN at 10 meters.
Peak wind was measured at a North Dakota DOT RWIS station.
Tree branches were toppled and partially uprooted. Time estimated from radar.
Large tree branches were broken and one tree was snapped.
Large 4 to 6 inch diameter branches broken down across town.
Peak wind gust measured at a RAWS station. Time estimated based on radar data.
The NDAWN 2E of Mayville reported a 58 mph wind gust.
Law enforcement reports large trees are down across the area.
Large tree branches broken, time estimated via radar.
Public report of downed trees and power lines.
Public report of hail via social media. Time estimate based on radar.
Peak wind gust measured at a personal weather station.
A tree was blown down, blocking Highway 32.
Peak wind of 63 mph was measured at KGFK.
Peak wind was measured at a North Dakota DOT RWIS station.
A semi truck was blown over along Interstate 29.
Relayed via broadcast media.
Large trees were snapped or uprooted. Timing based on radar analysis.
One foot diameter trees were blown down.
Semi truck was flipped over on Interstate 29.
Peak wind gust at 10 meters, reported via NDAWN.
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, 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: 969837, 969839, 969840, 969842, 969844, 969846, 969847, 969849, 969852, 969853, 969856, 969858, 969860, 969862, 969864, 969870, 969871, 969875, 969879, 969880, 969881, 969882, 969883, 969885, 969886, 969887, 969888, 969889, 969890, 969891, 969892, 969893, 969894, 969896, 969897, 969898, 969900.