Tornadoes:

Tornado - 4 E Erie Cass, ND Date 8/20/2021 Time (Local) 4:19 PM EF Rating 0 Est. Peak Winds 70 MPH Path Length Less than 0.25 mi Max Width 40 yd Injuries/Deaths 0/0 Summary: Brief touchdown reported via social media. Some tree branches and corn stalks were damaged. Track Map

The Enhanced Fujita (EF) Scale classifies tornadoes into the following categories:

EF0 Weak 65-85 mph	EF1 Moderate 86-110 mph	EF2 Significant 111-135 mph	EF3 Severe 136-165 mph	EF4 Extreme 166-200 mph	EF5 Catastrophic 200+ mph

Photos & Video

Photos and video of the mini supercells that prompted the tornado warnings

Extremely low wall cloud with occasional funnel-esque features along it, 3 miles west of Enderlin, ND #ndwx @NWSGrandForks @NWSBismarck pic.twitter.com/CO54sBnhvP

— Weather Unrated (@WxUnrated) August 20, 2021

Near Amenia. #VNLFirstAlert #ndwx pic.twitter.com/Obfyi9zOlY

— Eric Whitehill (@torchaser) August 20, 2021

Wow. @NWSGrandForks nw of casselton pic.twitter.com/TMteXh2kwz

— The Rear Flank 🎬 (@charliemizza) August 20, 2021

Hunter nd @NWSGrandForks @WDAYnews pic.twitter.com/MR3S8DRUsK

— The Rear Flank 🎬 (@charliemizza) August 20, 2021

Another attempt about to happen on top of norcross MN. evident rotation @NWSAberdeen pic.twitter.com/QsyTSgEWXu

— Chris_Wicklund (@Wicky_dubs_WX) August 20, 2021

Radar

This event had three tornado warnings and 5 severe thunderstorm warnings issued in the afternoon and early evening hours of August 20th.

The line that prompted severe thunderstorm warnings in Minnesota.	Reflectivity and Velocity of the tornado warned storm in Barnes, Griggs, and Steele counties	Reflectivity and Velocity of the tornado warned storm in Cass and Barnes counties

Storm Reports

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE GRAND FORKS ND
312 PM CDT WED AUG 25 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0116 PM     TSTM WND DMG     4 E HAZEL               48.02N 96.03W 
08/20/2021                   Pennington         MN   PUBLIC          

            FAUL ASK AND PINE TREES BROKEN DOWN IN A SHELTER BELT. 
            PHOTO AND REPORT POSTED VIA SOCIAL MEDIA. TIME ESTIMATED 
            BASED ON RADAR

0155 PM     TSTM WND DMG     5 ESE HIGH LANDING      48.02N 95.71W 
08/20/2021                   Pennington         MN   PUBLIC          

            TIN ROOF PANEL BLOWN OFF A SHED. 

0234 PM     FUNNEL CLOUD     6 WNW ENDERLIN          46.66N 97.72W 
08/20/2021                   Barnes             ND   TRAINED SPOTTER 

            PERSISTENT AND LOW WALL CLOUD WITH POSSIBLE FUNNEL. PHOTO
            AND REPORT POSTED VIA SOCIAL MEDIA.

0325 PM     TSTM WND GST     1 NW BAUDETTE           48.72N 94.60W 
08/20/2021  M52.00 MPH       Lake Of The Woods  MN   ASOS            

            PEAK WIND MEASURED AT THE BAUDETTE INTERNATIONAL AIRPORT 
            /KBDE/.

0418 PM     TORNADO          4 E ERIE                47.11N 97.30W 
08/20/2021  F0               Cass               ND   TRAINED SPOTTER 

            A FUNNEL WITH BRIEF TOUCHDOWN. REPORT POSTED VIA SOCIAL 
            MEDIA. SOME TREE BRANCHES AND CORN STALKS WERE SEEN 
            SWIRLING IN THE DEBRIS. PEAK WINDS ESTIMATED TO 70 MPH. 
            MAXIMUM WIDTH TO 40 YARDS. TRACK LENGTH OF LESS THAN ONE 
            QUARTER MILE TO THE EAST-NORTHEAST BY 419 PM CDT.

0432 PM     FUNNEL CLOUD     6 NNW LUVERNE           47.33N 97.98W 
08/20/2021                   Steele             ND   TRAINED SPOTTER 

            PERSISTENT WALL CLOUD WITH BRIEF FUNNEL.

0505 PM     TSTM WND GST     1 W CUMMINGS            47.51N 97.10W 
08/20/2021  E70.00 MPH       Traill             ND   TRAINED SPOTTER 

0525 PM     TSTM WND DMG     2 N ALMORA              46.28N 95.37W 
08/20/2021                   Otter Tail         MN   PUBLIC          

            LARGE TREE BLOWN DOWN. TIME ESTIMATED BASED ON RADAR.

0530 PM     TSTM WND DMG     5 W ELDRED              47.68N 96.89W 
08/20/2021                   Polk               MN   PUBLIC          

            LARGE ASH AND COTTONWOOD BRANCHES BLOWN DOWN IN A SHELTER
            BELT. TIME ESTIMATED BASED ON RADAR.

0645 PM     NON-TSTM WND GST 2 N MADDOCK             47.99N 99.53W 
08/20/2021  M60.00 MPH       Benson             ND   MESONET         

            PEAK WIND MEASURED AT AN NDAWN STATION MEASURED AT 10 
            METERS.

0723 PM     NON-TSTM WND GST 6 ESE LEEDS             48.26N 99.32W 
08/20/2021  M63.00 MPH       Benson             ND   MESONET         

            PEAK WIND MEASURED AT THE NDAWN STATIONS NILES 3SE AT 10 
            METERS.

0816 PM     NON-TSTM WND GST 4 SSW DEVILS LAKE       48.06N 98.91W 
08/20/2021  M55.00 MPH       Ramsey             ND   MESONET         

            SUSTAINED AT 45 GUSTING TO 55 MPH AT THE RWIS STATION ON 
            HIGHWAY 20 AT MP98.


&&

$$ 

Rain Reports

 Public Information Statement
National Weather Service Grand Forks ND
1122 AM CDT Sat Aug 21 2021

...PRECIPITATION REPORTS...

Location                     Amount    Time/Date       Provider
Pelican Rapids               4.88 in   0810 AM 08/21   Public
3 NNW Huntersville           3.80 in   0953 AM 08/21   Public
Roseau                       3.45 in   0810 AM 08/21   Public
Wadena                       3.25 in   0955 AM 08/21   Public
Thief River Falls            2.90 in   0935 AM 08/21   Public
Wadena                       2.88 in   1100 PM 08/20   Public
Park Rapids                  2.75 in   0200 AM 08/21   Public
Park Rapids AP MN            2.73 in   0553 AM 08/21   ASOS
Roseau MN 2 E                2.73 in   0408 AM 08/21   RAWS
Fertile MN 0.6 E             2.71 in   0300 AM 08/21   COCORAHS
Badoura MN 2 E               2.53 in   0406 AM 08/21   RAWS
2 SE Menahga                 2.50 in   0748 PM 08/20   Public
Glacial Ridge Portable       2.49 in   0532 AM 08/21   RAWS
Grand Forks ND 2.5 SE        2.40 in   0200 PM 08/20   COCORAHS
Roseau MN                    2.40 in   0530 AM 08/21   HADS
Thorhult MN                  2.40 in   0500 PM 08/20   COOP
Holt MN 6 E                  2.26 in   0530 AM 08/21   HADS
Badoura MN 1 SE              2.25 in   0530 AM 08/21   HADS
Baudette MN 3 S              2.13 in   0406 AM 08/21   RAWS
2 WSW Fergus Falls           2.00 in   0756 PM 08/20   Public
3 WSW Holmes                 2.00 in   0136 PM 08/20   Trained Spotter
Baudette AP MN               1.93 in   0553 AM 08/21   ASOS
Fertile MN 3 WSW             1.90 in   0545 AM 08/21   HADS
Baudette MN 12 S             1.83 in   0515 AM 08/21   HADS
2 ESE Bygland                1.83 in   0100 AM 08/21   Public
Buxton ND 4 ENE              1.80 in   0600 AM 08/21   AWS
Bemidji                      1.69 in   0805 AM 08/21   Public
Moorhead                     1.66 in   0124 AM 08/21   Broadcast Media
Fergus Falls MN 3 W          1.65 in   0545 AM 08/21   HADS
Elizabeth MN 2 NNE           1.63 in   0600 AM 08/21   CWOP
Alvarado MN 5 NNE            1.62 in   0600 AM 08/21   AWS
Fargo ND 7 SW                1.61 in   0552 AM 08/21   CWOP
West Fargo                   1.60 in   0824 PM 08/20   Public
Fergus Falls MN              1.57 in   0559 AM 08/21   CWOP
Hope ND 5.4 WNW              1.54 in   0945 PM 08/20   COCORAHS
Walhalla ND 3 NNE            1.54 in   0600 AM 08/21   AWS
Bemidji MN 8 N               1.51 in   0600 AM 08/21   CWOP
Fargo ND 3.6 NNE             1.43 in   0720 PM 08/20   COCORAHS
Moorhead MN 1 NE             1.42 in   0555 AM 08/21   CWOP
Holt MN 15 E                 1.41 in   0520 AM 08/21   RAWS
Lake Park MN 7.9 S           1.40 in   0630 PM 08/20   COCORAHS
2 S Oberon                   1.40 in   1047 AM 08/20   Public
Grand Forks ND 7 SW          1.32 in   0600 AM 08/21   CWOP
Fargo 1.2 ESE                1.30 in   0700 PM 08/20   COCORAHS
Fargo AP ND                  1.29 in   0553 AM 08/21   ASOS
Florian MN 1 S               1.28 in   0545 AM 08/21   HADS
Mentor MN 2 SW               1.28 in   0558 AM 08/21   CWOP
Arygle MN 12 WNW             1.23 in   0600 AM 08/21   CWOP
Fort Totten ND 5 ENE         1.21 in   0551 AM 08/21   RAWS
Hatton ND 2 S                1.21 in   0600 AM 08/21   AWS
Highlanding MN 20 E          1.21 in   0530 AM 08/21   HADS
Thief River Falls MN 2 W     1.20 in   0600 AM 08/21   AWS
Grand Forks AP ND            1.19 in   0553 AM 08/21   ASOS
Northcote MN 2 ENE           1.19 in   0545 AM 08/21   HADS
Hallock AP MN                1.17 in   0555 AM 08/21   AWOS
Hampden ND 3 SE              1.17 in   0458 AM 08/21   RAWS
Glyndon MN 2 NW              1.14 in   0545 AM 08/21   HADS
Grygla MN 6 WNW              1.13 in   0530 AM 08/21   HADS
Frazee MN 3 E                1.12 in   0555 AM 08/21   CWOP
Bemidji MN 5 N               1.10 in   0605 AM 08/21   AWS
Osage MN 5 NW                1.08 in   0530 AM 08/21   HADS
Cooperstown ND 5 E           1.05 in   0500 AM 08/21   HADS
Bemidji MN 2 WNW             1.04 in   0406 AM 08/21   RAWS
Malung MN 1 NW               1.03 in   0530 AM 08/21   HADS
Glyndon MN 2 N               0.99 in   0545 AM 08/21   HADS
Alvarado MN 1 N              0.98 in   0530 AM 08/21   HADS
Cormorant MN 5 NW            0.97 in   0600 AM 08/21   AWS
Rlnm5                        0.96 in   0409 AM 08/21   RAWS
Gonvick MN                   0.93 in   0555 AM 08/21   CWOP
Detroit Lakes MN 1 N         0.92 in   0520 AM 08/21   RAWS
Webster ND                   0.92 in   0600 AM 08/21   AWS
Mahnomen 1 SE MN             0.91 in   0545 AM 08/21   HADS
Detroit Lakes MN 5.7 N       0.90 in   0430 AM 08/21   COCORAHS
Harwood ND                   0.89 in   0545 AM 08/21   CWOP
Lake Itasca MN 2 SE          0.86 in   0407 AM 08/21   RAWS
Bagley MN                    0.84 in   0605 AM 08/21   AWS
Warroad MN                   0.81 in   0530 AM 08/21   HADS
Walhalla ND 3.6 SSE          0.76 in   0600 AM 08/21   COCORAHS
Bemidji AP MN                0.75 in   0555 AM 08/21   AWOS
Brooks MN 3 WNW              0.74 in   0545 AM 08/21   HADS
Grand Forks ND AFB           0.74 in   0556 AM 08/21   ASOS
Devils Lake ND               0.69 in   0559 AM 08/21   CWOP
Leeds ND 4 SE                0.69 in   0515 AM 08/21   HADS
Thief River Falls AP MN      0.69 in   0556 AM 08/21   AWOS
Staples AP MN                0.68 in   0555 AM 08/21   AWOS
Michigan ND                  0.67 in   0500 AM 08/21   COOP
Norcross MN 1 NW             0.67 in   0500 AM 08/21   HADS
Lisbon ND 18 E               0.66 in   0549 AM 08/21   RAWS
Bagley MN 5 N                0.65 in   0555 AM 08/21   CWOP
Brooks MN                    0.63 in   0605 PM 08/20   AWS
Dakota Junction MN 1 WSW     0.62 in   0605 PM 08/20   AWS
Mentor MN 9 W                0.62 in   0600 AM 08/21   HADS
Felton MN 8 NE               0.61 in   0545 AM 08/21   HADS
Karlstad MN                  0.61 in   0406 AM 08/21   RAWS
Red Lake Falls MN            0.60 in   0530 AM 08/21   HADS
Warren MN 3 ENE              0.60 in   0545 AM 08/21   HADS
Clemenston MN                0.59 in   0500 AM 08/21   HADS
Campbell MN                  0.51 in   0530 AM 08/21   HADS

Observations are collected from a variety of sources with varying
equipment and exposures. We thank all volunteer weather observers
for their dedication. Not all data listed are considered official.

$$ 

Environment

Synoptic environment:

300mb analysis	Potential Vorticity	18Z Sounding from ABR

Near-storm environment:

Surface-Based CAPE	Effective Bulk Shear	Supercell Composite Parameter

Additional environmental data:

WPC Surface Analysis from 12Z August 20th through 00Z August 21st

Issued at 103 PM CDT Fri Aug 20 2021

Storms continue to track northeastward, with the bulk of the 
activity pushing past the international border as expected. Primary 
concern in the near term is the line of storms in northwest 
Minnesota exhibiting some QLCS-like qualities. With 0-3km shear 
vectors pointed perpendicular to portions of the line, this region 
may be an area to watch over the next few hours for brief tornadoes.

Looking at surface analysis, the surface low has begun to deepen and 
appears to be centered over central North Dakota with the cold front 
draping southward just east of Bismarck, with a warm front/theta-e 
gradient stretching across the central Red River Valley and turning 
northward. An area of clearing clouds has begun to enter North 
Dakota, destabilizing the air-mass beneath. Within this area of 
clearing, a plume of modest MLCAPE (around 1500-2000 J/kg in the 
south Red River Valley) has begun to filter in. Areas of cumulus are 
already being seen on satellite within the south Valley with a few 
showers cropping up. Notably, within the south RRV and into NE South 
Dakota, showers have begun to form along what appears to be a 
boundary of differential diabatic heating, fueling near surface 
destabilization and creating what appears to be some sort of 
boundary. Moderate effective bulk shear (35-40 knots) exists across 
the area, favoring some storm organization this afternoon.

Looking at model derived soundings, hodographs appear favorable for 
some tornado potential this afternoon. While not the textbook hook 
hodographs typical for tornadoes, there is a low level area of 
veering within the warm sector that could provide an environment for 
tornado development this afternoon. On top of that, with the cold 
front upstream creating pre-existing vorticity, the potential is 
still on track for tornadoes. Hail and damaging winds remain a 
concern as well from the strongest storms this afternoon. 
Observational trends will have to be monitored to be more specific 
on threat areas, but at this time most areas still remain under the 
threat for severe weather this afternoon.

&&

Issued at 332 PM CDT Fri Aug 20 2021

Current concerns over the next few hours will be the potential for 
mini supercells in the south valley south of the warm front and near 
the pressure trough, and convection along the cold front to the 
west. Increased convective coverage is expected as the bulk of 
forcing pushes northeastward.

Line of storms continues to advect northeastward in northwest 
Minnesota crossing out of the CWA within the next hour or two. 
Concern now shifts towards southeast North Dakota where what appears 
to be a pre-frontal trough has begun to take shape over the area and 
is well within the vicinity of the warm front. As of 20z, a mini 
supercell has developed northwest of Enderlin.

Surface analysis continues to show broad cyclonic circulation 
centered in southeast North Dakota. Attached to it remains the cold 
front stretching southward into South Dakota, with a warm front that 
stretches across the RRV before jutting northward into Canada. A 
pressure trough was also noted, with 1001-1002mb being reported in 
NE SD. In this area, moderate instability exists with 2000+ J/kg of 
MLCAPE and effective bulk shear values approaching 40+ knots, 
supporting the development of mid level mesocyclones. There is a 
concern with these individual storms that have developed across the 
south valley to potentially become mini-supercells, as there is 
likely an area of enhanced cyclonic flow and vorticity within this 
region and the close proximity to the warm front facilitating 
localized increases in SRH. Effective layer STP values are also 
starting to filter in above one across the region. Putting all of 
this together, there is the potential for mini supercell development 
with the threat for tornadoes.

Gazing back further west, the cold front continues to push east-
northeastward, and is already providing a focused area of convection 
to our west. The expectation is for this threat along the cold front 
to continue, as meaningful instability remains well in place within 
the warm sector, and there isn't any expectation at this time for 
the mini-supercells to scour that out.

Finally, as the bulk of the forcing continues northeastward, the 
expectation is for convective coverage to increase in the valley. 
All hazards remain possible at this time, including tornadoes. 
Trends will continue to be monitored for potential more development 
in the central valley over the next few hours as well as monitoring 
of the convection near the cold front.

&&