Thunderstorms flared up across southern Cass County (North Dakota) on the afternoon of August 26th, dropping some large hail. After a several hour break, another storm intensified and dropped large hail over north central Becker and southern Mahnomen counties in Minnesota. Then after 8 pm CDT, a line of storms from north central North Dakota spread into the Devils Lake region. These storms produced damaging wind gusts. After 9 pm CDT, another line of storms formed ahead of the Devils Lake line, and these also tracked to the east. This line brought hail and damaging wind gusts to the Valley City and Grand Forks areas. Eventually, both lines of storms moved into the central and northern Red River Valley, then progressed into northwest Minnesota. As they did, they continued to produce damaging winds. Within the lines, several long track tornadoes also formed. Both of these occurred from the northeast corner of Norman County up toward the Lower Red Lake in Minnesota. Quite a bit of tree damage resulted along this track.

Thunderstorm Wind in PEMBINA, NORTH DAKOTA
From 26-AUG-18 21:42:00 to 26-AUG-18 21:42:00 (CST-6)
Location: BOWESMONT
Magnitude: 57.00 MG
Reported by: Mesonet

The wind gust was measured by a North Dakota DOT RWIS sensor along Interstate 29.

Thunderstorm Wind in PEMBINA, NORTH DAKOTA
From 26-AUG-18 21:09:00 to 26-AUG-18 21:09:00 (CST-6)
Location: HALLSON
Magnitude: 56.00 MG
Reported by: Mesonet

The wind gust was measured by a personal weather station.

Thunderstorm Wind in RAMSEY, NORTH DAKOTA
From 26-AUG-18 20:10:00 to 26-AUG-18 20:10:00 (CST-6)
Location: HAMPDEN
Magnitude: 56.00 MG
Reported by: Mesonet

The wind gust was measured by a RAWS station.

Thunderstorm Wind in RAMSEY, NORTH DAKOTA
From 26-AUG-18 20:12:00 to 26-AUG-18 20:12:00 (CST-6)
Location: CAMP GRAFTON
Magnitude: 54.00 MG
Reported by: Mesonet

The wind gust was measured by a North Dakota DOT RWIS site.

Hail in BARNES, NORTH DAKOTA
From 26-AUG-18 20:16:00 to 26-AUG-18 20:16:00 (CST-6)
Location: LITCHVILLE
Magnitude: 1.00 
Reported by: Public

Hail in CASS, NORTH DAKOTA
From 26-AUG-18 14:35:00 to 26-AUG-18 14:35:00 (CST-6)
Location: FARGO
Magnitude: 1.00 
Reported by: Public

Hail in BARNES, NORTH DAKOTA
From 26-AUG-18 20:40:00 to 26-AUG-18 20:40:00 (CST-6)
Location: VALLEY CITY
Magnitude: 0.75 
Reported by: Public

Thunderstorm Wind in PEMBINA, NORTH DAKOTA
From 26-AUG-18 21:10:00 to 26-AUG-18 21:10:00 (CST-6)
Location: CAVALIER ARPT
Magnitude: 50.00 MG
Reported by: Mesonet

The wind gust was measured at the Cavalier airport.

Thunderstorm Wind in CAVALIER, NORTH DAKOTA
From 26-AUG-18 20:35:00 to 26-AUG-18 20:35:00 (CST-6)
Location: MT CARMEL
Magnitude: 56.00 EG
Reported by: Emergency Manager

Six inch diameter branches were blown down.

Thunderstorm Wind in GRAND FORKS, NORTH DAKOTA
From 26-AUG-18 21:15:00 to 26-AUG-18 21:15:00 (CST-6)
Location: MERRIFIELD
Magnitude: 55.00 EG
Reported by: NWS Employee

Several 3 to 6 inch diameter trees and branches were snapped across the south end of the city of Grand Forks.

Thunderstorm Wind in PEMBINA, NORTH DAKOTA
From 26-AUG-18 21:25:00 to 26-AUG-18 21:25:00 (CST-6)
Location: HAMILTON
Magnitude: 62.00 MG
Reported by: Mesonet

The wind gust was measured by a personal weather station.

Thunderstorm Wind in WALSH, NORTH DAKOTA
From 26-AUG-18 21:30:00 to 26-AUG-18 21:30:00 (CST-6)
Location: GRAFTON
Magnitude: 60.00 EG
Reported by: Emergency Manager

A large tree was blown down.

Thunderstorm Wind in PEMBINA, NORTH DAKOTA
From 26-AUG-18 21:36:00 to 26-AUG-18 21:36:00 (CST-6)
Location: PEMBINA
Magnitude: 60.00 EG
Reported by: COOP Observer

Strong winds blew down trees and branches, which knocked out power for most of Pembina. A semi south of town was also tipped over in the northbound lane of Interstate 29.