A southwest flow aloft in conjunction with afternoon heating and an approaching short-wave trough resulted in the development of severe thunderstorms across Southeast Montana. A supercell produced softball size hail and a tornado in Powder River County.

Thunderstorm Wind in POWDER RIVER, MONTANA
From 03-AUG-13 18:59:00 to 03-AUG-13 18:59:00 (MST-7)
Location: BIDDLE
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A wind gust estimated at 65 mph was reported 10 miles north of Biddle.

Hail in CUSTER, MONTANA
From 03-AUG-13 19:30:00 to 03-AUG-13 19:30:00 (MST-7)
Location: TUSLER
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CUSTER, MONTANA
From 03-AUG-13 19:30:00 to 03-AUG-13 19:30:00 (MST-7)
Location: MURN
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in POWDER RIVER, MONTANA
From 03-AUG-13 21:00:00 to 03-AUG-13 21:00:00 (MST-7)
Location: BAY HOPE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Flash Flood in POWDER RIVER, MONTANA
From 03-AUG-13 17:25:00 to 03-AUG-13 19:30:00 (MST-7)
Location: SONNETTE
Flood cause: Heavy Rain / Burn Area
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Park/Forest Service

A severe thunderstorm producing very heavy rain and large amounts of hail moved through the East Fork of Otter Creek in the Ash Fire burn scar area during the early evening hours of the 3rd.
A reservoir was lost due to a blow out and numerous sections of freshly graveled roads in a BAER treatment area were washed out. In addition, large walls of hail were mixed with debris and ash which formed an insulation allowing the hail to stay frozen for a considerable length of time. The walls of hail were about 6 feet deep and extended 10 to 12 feet in width on both sides of a channel.

Tornado in POWDER RIVER, MONTANA
From 03-AUG-13 18:15:00 to 03-AUG-13 18:20:00 (MST-7)
Location: EPSIE
Tornado F-scale: EF0
Reported by: Emergency Manager

The tornado was reported just west of Wolf Mountain and north of Post, Montana and Rough Creek. There was plenty of debris along with hail damage east of town along Highway 59. Hail accompanied the supercell thunderstorm and was reported to be golf ball to softball size.

Hail in POWDER RIVER, MONTANA
From 03-AUG-13 18:35:00 to 03-AUG-13 18:35:00 (MST-7)
Location: (4BQ)BROADUS ARPT
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CUSTER, MONTANA
From 03-AUG-13 18:52:00 to 03-AUG-13 18:52:00 (MST-7)
Location: TUSLER
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

All the windows and siding on the north side of a house, shop, and camper were damaged. A pickup window was also broken.

Hail in BIG HORN, MONTANA
From 03-AUG-13 17:15:00 to 03-AUG-13 17:15:00 (MST-7)
Location: DECKER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in POWDER RIVER, MONTANA
From 03-AUG-13 17:15:00 to 03-AUG-13 17:15:00 (MST-7)
Location: COALWOOD
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Hail in BIG HORN, MONTANA
From 03-AUG-13 17:35:00 to 03-AUG-13 17:35:00 (MST-7)
Location: DECKER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in POWDER RIVER, MONTANA
From 03-AUG-13 17:57:00 to 03-AUG-13 17:57:00 (MST-7)
Location: SONNETTE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in POWDER RIVER, MONTANA
From 03-AUG-13 18:13:00 to 03-AUG-13 18:13:00 (MST-7)
Location: OLIVE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Funnel Cloud in POWDER RIVER, MONTANA
From 03-AUG-13 18:15:00 to 03-AUG-13 18:15:00 (MST-7)
Location: BROADUS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Funnel Cloud in POWDER RIVER, MONTANA
From 03-AUG-13 18:15:00 to 03-AUG-13 18:15:00 (MST-7)
Location: (4BQ)BROADUS ARPT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in POWDER RIVER, MONTANA
From 03-AUG-13 18:20:00 to 03-AUG-13 18:20:00 (MST-7)
Location: (4BQ)BROADUS ARPT
Magnitude: 4.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in ROSEBUD, MONTANA
From 03-AUG-13 18:30:00 to 03-AUG-13 18:30:00 (MST-7)
Location: ANGELA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in BIG HORN, MONTANA
From 03-AUG-13 17:15:00 to 03-AUG-13 17:15:00 (MST-7)
Location: DECKER
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A wind gust of 60 mph was estimated just north of the Tongue River Reservoir.

Hail in POWDER RIVER, MONTANA
From 03-AUG-13 18:59:00 to 03-AUG-13 18:59:00 (MST-7)
Location: BIDDLE
Magnitude: 2.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter