A low pressure trough and advancing cold front from the west interacted with a hot and humid air mass to generate mid-day strong to severe thunderstorms which strengthened into a large and damaging supercell through the afternoon hours and moved toward the east and southeast.

Hail in ROOSEVELT, MONTANA
From 21-JUL-18 14:44:00 to 21-JUL-18 14:44:00 (MST-7)
Location: FROID
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported, via social media, ping pong ball size hail and broken windows on the north side of their house.

Thunderstorm Wind in ROOSEVELT, MONTANA
From 21-JUL-18 14:50:00 to 21-JUL-18 14:50:00 (MST-7)
Location: FROID
Magnitude: 76.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported, via social media, 87 mph wind gusts measured by a personal weather station, and heavy rain.

Hail in ROOSEVELT, MONTANA
From 21-JUL-18 14:55:00 to 21-JUL-18 14:55:00 (MST-7)
Location: FROID
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported, via social media, hen egg size hail and extensive tree damage.

Thunderstorm Wind in ROOSEVELT, MONTANA
From 21-JUL-18 14:56:00 to 21-JUL-18 14:56:00 (MST-7)
Location: FROID
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public estimated 60 mph wind gusts.

Hail in ROOSEVELT, MONTANA
From 21-JUL-18 14:56:00 to 21-JUL-18 14:56:00 (MST-7)
Location: FROID
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported quarter size hail.

Hail in VALLEY, MONTANA
From 21-JUL-18 11:27:00 to 21-JUL-18 11:27:00 (MST-7)
Location: OPHEIM
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported quarter size hail.

Hail in VALLEY, MONTANA
From 21-JUL-18 11:34:00 to 21-JUL-18 11:34:00 (MST-7)
Location: OPHEIM
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported quarter size hail.

Hail in VALLEY, MONTANA
From 21-JUL-18 12:12:00 to 21-JUL-18 12:12:00 (MST-7)
Location: GLENTANA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported quarter size hail.

Hail in ROOSEVELT, MONTANA
From 21-JUL-18 12:22:00 to 21-JUL-18 12:22:00 (MST-7)
Location: FROID
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported ping pong ball size hail.

Hail in SHERIDAN, MONTANA
From 21-JUL-18 12:25:00 to 21-JUL-18 12:25:00 (MST-7)
Location: REDSTONE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported golf ball size hail.

Hail in DANIELS, MONTANA
From 21-JUL-18 12:33:00 to 21-JUL-18 12:33:00 (MST-7)
Location: PEERLESS
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported hail up to the size of golf balls.  Time estimated from radar.

Hail in DANIELS, MONTANA
From 21-JUL-18 12:47:00 to 21-JUL-18 12:47:00 (MST-7)
Location: PEERLESS
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported golf ball size hail.

Thunderstorm Wind in DANIELS, MONTANA
From 21-JUL-18 13:20:00 to 21-JUL-18 13:20:00 (MST-7)
Location: SCOBEY
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported 60 mph wind gusts.

Hail in DANIELS, MONTANA
From 21-JUL-18 13:20:00 to 21-JUL-18 13:20:00 (MST-7)
Location: SCOBEY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported quarter size hail.

Hail in DANIELS, MONTANA
From 21-JUL-18 13:51:00 to 21-JUL-18 13:51:00 (MST-7)
Location: FLAXVILLE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported quarter size hail.

Thunderstorm Wind in ROOSEVELT, MONTANA
From 21-JUL-18 14:26:00 to 21-JUL-18 14:26:00 (MST-7)
Location: FT KIPP
Magnitude: 65.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported, via social media, several farm outbuildings severely damaged or destroyed.  Time estimated by radar.

Thunderstorm Wind in ROOSEVELT, MONTANA
From 21-JUL-18 14:40:00 to 21-JUL-18 14:40:00 (MST-7)
Location: FROID
Magnitude: 90.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public measured sustained winds of 87 mph and a peak wind gust of 103 mph at a trusted an accurate personal weather station.  Time estimated from radar.

Thunderstorm Wind in ROOSEVELT, MONTANA
From 21-JUL-18 15:00:00 to 21-JUL-18 15:00:00 (MST-7)
Location: FT KIPP
Magnitude: 53.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported, via social media, 61 mph wind gusts.

Hail in ROOSEVELT, MONTANA
From 21-JUL-18 15:00:00 to 21-JUL-18 15:00:00 (MST-7)
Location: BROCKTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported quarter size hail and a damaged outdoor swing set.

Hail in ROOSEVELT, MONTANA
From 21-JUL-18 15:11:00 to 21-JUL-18 15:11:00 (MST-7)
Location: FROID
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported, via social media, golf ball size hail.

Thunderstorm Wind in ROOSEVELT, MONTANA
From 21-JUL-18 15:15:00 to 21-JUL-18 15:15:00 (MST-7)
Location: CULBERTSON
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported 60 mph wind gusts.

Hail in ROOSEVELT, MONTANA
From 21-JUL-18 15:15:00 to 21-JUL-18 15:15:00 (MST-7)
Location: CULBERTSON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported quarter size hail.

Thunderstorm Wind in ROOSEVELT, MONTANA
From 21-JUL-18 15:19:00 to 21-JUL-18 15:19:00 (MST-7)
Location: BAINVILLE
Magnitude: 65.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Roosevelt County Emergency Manager reported ten to eleven empty BNSF train cars derailed.

Hail in ROOSEVELT, MONTANA
From 21-JUL-18 15:30:00 to 21-JUL-18 15:30:00 (MST-7)
Location: BAINVILLE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Pubic reported, via social media, golf ball size hail.

Thunderstorm Wind in RICHLAND, MONTANA
From 21-JUL-18 16:05:00 to 21-JUL-18 16:05:00 (MST-7)
Location: SIOUX PASS DOT
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public estimated 70 mph wind gusts.

Thunderstorm Wind in RICHLAND, MONTANA
From 21-JUL-18 16:33:00 to 21-JUL-18 16:33:00 (MST-7)
Location: SIDNEY AIRPORT (KSDY)
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Sidney airport AWOS site measured 58 mph wind gusts.