Strong, southeasterly low level winds ahead of a surface low resulted in dew points rising into the 50s to near 60 degrees across southeast Montana. This, combined with steep, mid-level lapse rates,  ahead of an upper level disturbance approaching from the Great Basin area resulted in the development of severe thunderstorms across much of the Billings Forecast Area.

Hail in CUSTER, MONTANA
From 20-MAY-20 15:34:00 to 20-MAY-20 15:34:00 (MST-7)
Location: VOLBORG
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Hail in CUSTER, MONTANA
From 20-MAY-20 16:25:00 to 20-MAY-20 16:25:00 (MST-7)
Location: MOON CREEK
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in CUSTER, MONTANA
From 20-MAY-20 16:30:00 to 20-MAY-20 16:30:00 (MST-7)
Location: FT KEOGH
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CUSTER, MONTANA
From 20-MAY-20 16:58:00 to 20-MAY-20 16:58:00 (MST-7)
Location: MILES CITY
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in CUSTER, MONTANA
From 20-MAY-20 16:58:00 to 20-MAY-20 16:58:00 (MST-7)
Location: MILES CITY
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A windshield was cracked.

Hail in CUSTER, MONTANA
From 20-MAY-20 17:05:00 to 20-MAY-20 17:05:00 (MST-7)
Location: MILES CITY
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in POWDER RIVER, MONTANA
From 20-MAY-20 17:05:00 to 20-MAY-20 17:05:00 (MST-7)
Location: BELLE CREEK ARPT
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CUSTER, MONTANA
From 20-MAY-20 17:09:00 to 20-MAY-20 17:09:00 (MST-7)
Location: KINSEY
Magnitude: 2.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in CUSTER, MONTANA
From 20-MAY-20 17:20:00 to 20-MAY-20 17:20:00 (MST-7)
Location: KINSEY
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

This storm produced a wall cloud. A storm chaser vehicle was destroyed on I-94.

Hail in CUSTER, MONTANA
From 20-MAY-20 17:30:00 to 20-MAY-20 17:30:00 (MST-7)
Location: KINSEY
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in CARTER, MONTANA
From 20-MAY-20 17:00:00 to 20-MAY-20 17:00:00 (MST-7)
Location: RIDGE
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Several barns and shelters were destroyed.

Thunderstorm Wind in POWDER RIVER, MONTANA
From 20-MAY-20 17:00:00 to 20-MAY-20 17:00:00 (MST-7)
Location: BIDDLE
Magnitude: 61.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Tree limbs 6 inches in diameter were downed. Several out buildings were damaged.

Thunderstorm Wind in ROSEBUD, MONTANA
From 20-MAY-20 18:00:00 to 20-MAY-20 18:00:00 (MST-7)
Location: HATHAWAY
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in CUSTER, MONTANA
From 20-MAY-20 18:26:00 to 20-MAY-20 18:26:00 (MST-7)
Location: KINSEY
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A semi tipped over on I-94. In addition, 1 foot diameter trees were downed.

Thunderstorm Wind in ROSEBUD, MONTANA
From 20-MAY-20 17:07:00 to 20-MAY-20 17:07:00 (MST-7)
Location: LAME DEER
Magnitude: 51.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Thunderstorm Wind in CARTER, MONTANA
From 20-MAY-20 17:19:00 to 20-MAY-20 17:19:00 (MST-7)
Location: RIDGEWAY
Magnitude: 51.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Thunderstorm Wind in ROSEBUD, MONTANA
From 20-MAY-20 18:10:00 to 20-MAY-20 18:10:00 (MST-7)
Location: INGOMAR
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in CUSTER, MONTANA
From 20-MAY-20 18:19:00 to 20-MAY-20 18:19:00 (MST-7)
Location: MILES CITY ARPT
Magnitude: 57.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

A wind gust of 66 mph was recorded at the Miles City Airport.

Thunderstorm Wind in ROSEBUD, MONTANA
From 20-MAY-20 18:38:00 to 20-MAY-20 18:38:00 (MST-7)
Location: ROCK SPGS
Magnitude: 65.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

A wind gust of 75 mph occurred 2 miles northwest of Rock Springs.

Hail in CUSTER, MONTANA
From 20-MAY-20 16:45:00 to 20-MAY-20 16:45:00 (MST-7)
Location: MILES CITY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in POWDER RIVER, MONTANA
From 20-MAY-20 16:50:00 to 20-MAY-20 16:50:00 (MST-7)
Location: BIDDLE
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A new roof under construction was blown off a house.