A very unstable atmosphere and strong shear interacted with an upper-level disturbance to produce morning, afternoon, and evening periods of severe thunderstorms.

Hail in MCCONE, MONTANA
From 31-AUG-11 18:30:00 to 31-AUG-11 18:30:00 (MST-7)
Location: VIDA
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reported slushy penny-sized stones.

Hail in ROOSEVELT, MONTANA
From 31-AUG-11 18:35:00 to 31-AUG-11 18:35:00 (MST-7)
Location: BREDETTE
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reported small amounts of penny-sized hail stones.

Thunderstorm Wind in VALLEY, MONTANA
From 31-AUG-11 02:15:00 to 31-AUG-11 02:15:00 (MST-7)
Location: OPHEIM
Magnitude: 74.00 EG
Property damage: 17.00K
Crop damage: 0.00K
Reported by: Public

Public reported a 60-foot radio tower bent in half and 4-inch diameter tree limbs broken.  Wind gusts of 85 mph estimated from EF-scale toolkit.

Thunderstorm Wind in MCCONE, MONTANA
From 31-AUG-11 17:51:00 to 31-AUG-11 17:51:00 (MST-7)
Location: FT PECK LAKE HANDAR
Magnitude: 57.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet measured a 66 mph wind gust.

Thunderstorm Wind in VALLEY, MONTANA
From 31-AUG-11 18:13:00 to 31-AUG-11 18:13:00 (MST-7)
Location: LUSTRE
Magnitude: 62.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter measured a 71 mph wind gust.

Thunderstorm Wind in RICHLAND, MONTANA
From 31-AUG-11 18:20:00 to 31-AUG-11 18:20:00 (MST-7)
Location: ENID
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter estimated 60 mph wind gusts and reported pea-sized hail stones.

Thunderstorm Wind in MCCONE, MONTANA
From 31-AUG-11 18:30:00 to 31-AUG-11 18:30:00 (MST-7)
Location: VIDA
Magnitude: 70.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter estimated 70 to 80 mph wind gusts.

Thunderstorm Wind in ROOSEVELT, MONTANA
From 31-AUG-11 18:35:00 to 31-AUG-11 18:35:00 (MST-7)
Location: BREDETTE
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter estimated wind gusts of 70 mph.

Thunderstorm Wind in ROOSEVELT, MONTANA
From 31-AUG-11 18:53:00 to 31-AUG-11 18:53:00 (MST-7)
Location: WOLF PT
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

ASOS measured sustained winds at 44 mph with a gust of 58 mph.

Thunderstorm Wind in DANIELS, MONTANA
From 31-AUG-11 18:55:00 to 31-AUG-11 18:55:00 (MST-7)
Location: SCOBEY
Magnitude: 55.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Hail in VALLEY, MONTANA
From 31-AUG-11 18:13:00 to 31-AUG-11 18:13:00 (MST-7)
Location: LUSTRE
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reported penny- to nickel-sized hail stones.

Hail in SHERIDAN, MONTANA
From 31-AUG-11 19:14:00 to 31-AUG-11 19:14:00 (MST-7)
Location: RESERVE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Storm chaser reported quarter-sized hail mixed with heavy rain.

Hail in SHERIDAN, MONTANA
From 31-AUG-11 19:25:00 to 31-AUG-11 19:25:00 (MST-7)
Location: RESERVE
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public estimated penny-sized hail stones.

Thunderstorm Wind in VALLEY, MONTANA
From 31-AUG-11 17:41:00 to 31-AUG-11 17:41:00 (MST-7)
Location: GLASGOW
Magnitude: 53.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Glasgow ASOS measured a 61 mph wind gust.

Thunderstorm Wind in VALLEY, MONTANA
From 31-AUG-11 18:00:00 to 31-AUG-11 18:00:00 (MST-7)
Location: OPHEIM
Magnitude: 61.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Observer also measured sustained winds between 40 and 60 mph.