A strong low pressure system and associated cold front moved into the Northern Rockies, creating a favorable environment for strong hail producing thunderstorms and heavy rain.  Flash flooding was reported in the city of Butte with this event as up to an inch of precipitation occurred in 30 to 45 minutes.  Hail up to the size of baseballs and strong winds nearing 70 mph were also observed.

Hail in SILVER BOW, MONTANA
From 06-AUG-09 15:20:00 to 06-AUG-09 15:25:00 (MST-7)
Location: MAIDEN ROCK
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Rain in SILVER BOW, MONTANA
From 06-AUG-09 14:31:00 to 06-AUG-09 14:55:00 (MST-7)
Location: BUTTE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Seven thenths of an inch of rain fell in 24 minutes at Bert Mooney Airport.

Thunderstorm Wind in SILVER BOW, MONTANA
From 06-AUG-09 13:54:00 to 06-AUG-09 13:59:00 (MST-7)
Location: EAST BUTTE
Magnitude: 60.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

The Elk Park Department of Transportation weather station measured a thunderstorm wind gust up to 69 mph.

Flash Flood in SILVER BOW, MONTANA
From 06-AUG-09 13:35:00 to 06-AUG-09 14:35:00 (MST-7)
Location: MAIDEN ROCK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Park/Forest Service

Heavy rain caused several Forest Service roads to be flooded.

Hail in SILVER BOW, MONTANA
From 06-AUG-09 13:15:00 to 06-AUG-09 13:25:00 (MST-7)
Location: MAIDEN ROCK
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Park/Forest Service

Thunderstorm Wind in SILVER BOW, MONTANA
From 06-AUG-09 16:00:00 to 06-AUG-09 16:05:00 (MST-7)
Location: (BTM)MOONEY ARPT BUT
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Extensive tree damage was caused by strong thunderstorm winds.  The winds were estimated to be between 55 to 60 mph.

Hail in SILVER BOW, MONTANA
From 06-AUG-09 14:05:00 to 06-AUG-09 14:10:00 (MST-7)
Location: BUTTE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in SILVER BOW, MONTANA
From 06-AUG-09 14:00:00 to 06-AUG-09 14:05:00 (MST-7)
Location: ROCKER
Magnitude: 2.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A member of the public reported 2.5 inch hail to the Silver Bow County Sheriff.

Hail in SILVER BOW, MONTANA
From 06-AUG-09 13:05:00 to 06-AUG-09 13:10:00 (MST-7)
Location: MAIDEN ROCK
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Quarter sized hail reported.

Hail in SILVER BOW, MONTANA
From 06-AUG-09 13:50:00 to 06-AUG-09 14:05:00 (MST-7)
Location: JANNEY
Magnitude: 1.00 
Property damage: 0.50K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported hail increasing in size.  The windows of the home were damaged. The large hail caused tree branches to be stripped.

Hail in SILVER BOW, MONTANA
From 06-AUG-09 14:00:00 to 06-AUG-09 15:10:00 (MST-7)
Location: JANNEY
Magnitude: 1.50 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported that the hail caused damage to the windows of his home as well as three vehicles.  Tree branches were stripped from the large hail.

Hail in SILVER BOW, MONTANA
From 06-AUG-09 14:10:00 to 06-AUG-09 14:15:00 (MST-7)
Location: (BTM)MOONEY ARPT BUT
Magnitude: 2.00 
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Public

Extensive hail damage to homes, roofs, and vehicles reported on Green Acres and Continental Drive near Butte.  Hail size ranged between 1.75 and two inches in diameter.  In addition, wind gusts were estimated up to 70 mph, which caused some tree branches to break.

Flash Flood in SILVER BOW, MONTANA
From 06-AUG-09 14:30:00 to 06-AUG-09 15:30:00 (MST-7)
Location: COLUMBIA GARDENS
Flood cause: Heavy Rain
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Utility Company

Flooding was reported on both Elm and Silverbow Street.  A few homes on Silverbow had flooding in their basements.  The Butte Plaza Mall parking lot was flooded, and strong winds caused water to flow into the doorways and walkways of the mall.

Heavy Rain in SILVER BOW, MONTANA
From 06-AUG-09 14:30:00 to 06-AUG-09 15:30:00 (MST-7)
Location: BUTTE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Utility Company

The Public Works Department reported .75 inch hail and estimated one inch of rain in about 30 minutes in Butte.  Water was flowing down the streets.