Large-scale ascent along with afternoon heating, with cooling/moistening aloft,  resulted in approximately 2000 J/kg of CAPE with little inhibition (CIN). This combined with some veering with height of winds and approximately 20-30 kt mid-level flow supported organized multicell and some supercell structures.

Thunderstorm Wind in FALLON, MONTANA
From 07-JUN-18 19:45:00 to 07-JUN-18 19:45:00 (MST-7)
Location: WILLARD
Magnitude: 61.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Thunderstorm Wind in CARTER, MONTANA
From 07-JUN-18 20:16:00 to 07-JUN-18 20:16:00 (MST-7)
Location: MILL IRON
Magnitude: 53.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CARTER, MONTANA
From 07-JUN-18 19:05:00 to 07-JUN-18 19:05:00 (MST-7)
Location: RIDGEWAY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in FALLON, MONTANA
From 07-JUN-18 19:32:00 to 07-JUN-18 19:32:00 (MST-7)
Location: WEBSTER
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Tornado in BIG HORN, MONTANA
From 07-JUN-18 16:40:00 to 07-JUN-18 16:45:00 (MST-7)
Location: KIRBY
Tornado F-scale: EF1
Reported by: Trained Spotter

The tornado damaged a 20 foot diameter grain bin and tossed it 250 yards. A trailer was also damaged and blown across a driveway. There was also minor damage to a house as the gutters were ripped off and some of the metal roofing torn off. In addition, numerous large trees were uprooted or snapped in half.

Hail in ROSEBUD, MONTANA
From 07-JUN-18 17:37:00 to 07-JUN-18 17:37:00 (MST-7)
Location: FORSYTH
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in ROSEBUD, MONTANA
From 07-JUN-18 17:37:00 to 07-JUN-18 17:37:00 (MST-7)
Location: FORSYTH
Magnitude: 56.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Power lines and trees were down.

Thunderstorm Wind in ROSEBUD, MONTANA
From 07-JUN-18 17:37:00 to 07-JUN-18 17:37:00 (MST-7)
Location: FORSYTH
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Power lines and trees were down.

Thunderstorm Wind in POWDER RIVER, MONTANA
From 07-JUN-18 17:40:00 to 07-JUN-18 17:40:00 (MST-7)
Location: OTTER
Magnitude: 64.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in CUSTER, MONTANA
From 07-JUN-18 18:02:00 to 07-JUN-18 18:02:00 (MST-7)
Location: MILES CITY ARPT
Magnitude: 53.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Hail in CUSTER, MONTANA
From 07-JUN-18 18:30:00 to 07-JUN-18 18:30:00 (MST-7)
Location: BONFIELD
Magnitude: 2.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Flash Flood in CUSTER, MONTANA
From 07-JUN-18 18:30:00 to 07-JUN-18 20:00:00 (MST-7)
Location: BONFIELD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Water was reported to be rushing across I-94 trapping some vehicles and pushing over fences. There was also considerable hail on I-94 resulting in hazardous road conditions.

Thunderstorm Wind in PARK, MONTANA
From 07-JUN-18 06:18:00 to 07-JUN-18 06:18:00 (MST-7)
Location: LIVINGSTN MISSION FL
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Thunderstorm Wind in ROSEBUD, MONTANA
From 07-JUN-18 17:30:00 to 07-JUN-18 17:30:00 (MST-7)
Location: FORSYTH
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Multiple large trees were blown down or broken resulting in closed roads. Trees were also on power lines causing power outages.

Hail in CARBON, MONTANA
From 07-JUN-18 13:50:00 to 07-JUN-18 13:50:00 (MST-7)
Location: ROBERTS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Hail in BIG HORN, MONTANA
From 07-JUN-18 15:55:00 to 07-JUN-18 15:55:00 (MST-7)
Location: HARDIN
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in BIG HORN, MONTANA
From 07-JUN-18 16:10:00 to 07-JUN-18 16:10:00 (MST-7)
Location: CROW AGENCY
Magnitude: 56.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Hail in YELLOWSTONE, MONTANA
From 07-JUN-18 16:08:00 to 07-JUN-18 16:08:00 (MST-7)
Location: CUSTER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Hail in BIG HORN, MONTANA
From 07-JUN-18 16:10:00 to 07-JUN-18 16:10:00 (MST-7)
Location: YELLOWTAIL
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in TREASURE, MONTANA
From 07-JUN-18 16:35:00 to 07-JUN-18 16:35:00 (MST-7)
Location: BIGHORN
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Hail in BIG HORN, MONTANA
From 07-JUN-18 16:57:00 to 07-JUN-18 16:57:00 (MST-7)
Location: KIRBY
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in ROSEBUD, MONTANA
From 07-JUN-18 17:19:00 to 07-JUN-18 17:19:00 (MST-7)
Location: ROSEBUD
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A cottonwood tree was downed blocking the south lane of Highway 447 south of Rosebud.

Thunderstorm Wind in ROSEBUD, MONTANA
From 07-JUN-18 17:25:00 to 07-JUN-18 17:25:00 (MST-7)
Location: ROSEBUD
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Broken highway signs on I-94 were reported.

Thunderstorm Wind in ROSEBUD, MONTANA
From 07-JUN-18 17:30:00 to 07-JUN-18 17:30:00 (MST-7)
Location: BIRNEY
Magnitude: 51.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Hail in CUSTER, MONTANA
From 07-JUN-18 17:30:00 to 07-JUN-18 17:30:00 (MST-7)
Location: KINSEY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter