A low pressure system off the southern Oregon coast Thursday moved slightly inland Friday remaining nearly stationary after that. Several disturbances in the flow affected portions of Central and Southwest Montana. Strong lift over northwest portions of Central Montana during the evening, combined with a fairly unstable airmass and strong wind shear, aided in development of thunderstorms that included a threat of gusty winds, small hail, and brief heavy rain.

Hail in CASCADE, MONTANA
From 06-SEP-13 16:00:00 to 06-SEP-13 16:00:00 (MST-7)
Location: CALVERT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail measuring 1.00 inches (quarter sized) and brief heavy rain were reported.

Hail in TETON, MONTANA
From 06-SEP-13 18:33:00 to 06-SEP-13 18:33:00 (MST-7)
Location: COLLINS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail measuring 1.00 inches (quarter sized) was reported covering the ground. Brief heavy rain was also reported.

Hail in LEWIS AND CLARK, MONTANA
From 07-SEP-13 17:35:00 to 07-SEP-13 17:35:00 (MST-7)
Location: LINCOLN
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail measuring 1.50 inches (ping pong ball sized) and heavy rain were reported.

Hail in CASCADE, MONTANA
From 07-SEP-13 18:00:00 to 07-SEP-13 18:00:00 (MST-7)
Location: NIEHART
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail measuring 1.00 inches (quarter sized) was reported near Neihart, MT.

Heavy Rain in FERGUS, MONTANA
From 06-SEP-13 15:35:00 to 06-SEP-13 15:35:00 (MST-7)
Location: SPRING CREEK JCT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Rain measuring 2.10 inches in 40 minutes reported.

Heavy Rain in GLACIER, MONTANA
From 06-SEP-13 16:21:00 to 06-SEP-13 16:56:00 (MST-7)
Location: CUTBANK ARPT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Rain measuring 0.82 inches in 25 minutes.

Heavy Rain in GLACIER, MONTANA
From 06-SEP-13 05:30:00 to 07-SEP-13 05:30:00 (MST-7)
Location: FAMILY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Heavy rain measuring 3.20 inches in 24 hours. An 8X12 wood framed greenhouse was also blown over.

Thunderstorm Wind in CASCADE, MONTANA
From 05-SEP-13 15:13:00 to 05-SEP-13 15:13:00 (MST-7)
Location: (GTF)GREAT FALLS ARPT
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Strong winds estimated at 50KT (58MPH) snapped a tree 8-10 inches in diameter.

Thunderstorm Wind in JEFFERSON, MONTANA
From 05-SEP-13 18:00:00 to 05-SEP-13 18:00:00 (MST-7)
Location: WHITEHALL
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Strong winds estimated 50KT (58MPH) causing vehicle rollover on Interstate 90, mobile home damage, and numerous reports of roof and power line damage.

Thunderstorm Wind in CASCADE, MONTANA
From 05-SEP-13 15:13:00 to 05-SEP-13 15:13:00 (MST-7)
Location: (GTF)GREAT FALLS ARPT
Magnitude: 54.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

High winds measuring 54KT (62MPH) reported at the Great Falls Airport ASOS.

Thunderstorm Wind in CHOUTEAU, MONTANA
From 05-SEP-13 15:55:00 to 05-SEP-13 15:55:00 (MST-7)
Location: FLOWEREE
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

High winds measuring 52KT (60MPH).

Thunderstorm Wind in HILL, MONTANA
From 05-SEP-13 17:57:00 to 05-SEP-13 17:57:00 (MST-7)
Location: RUDYARD
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

High winds measuring 52KT (60MPH).

Thunderstorm Wind in HILL, MONTANA
From 05-SEP-13 17:57:00 to 05-SEP-13 17:57:00 (MST-7)
Location: COLD STONE
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

High winds measuring 52KT (60MPH).

Thunderstorm Wind in JEFFERSON, MONTANA
From 05-SEP-13 17:50:00 to 05-SEP-13 17:50:00 (MST-7)
Location: PIEDMONT
Magnitude: 57.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

High winds measuring 57KT (66MPH) reported at the Whitehall RAWS.

Thunderstorm Wind in JEFFERSON, MONTANA
From 05-SEP-13 18:32:00 to 05-SEP-13 18:32:00 (MST-7)
Location: BOULDER ARPT
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

High winds estimated at 52KT (60MPH) along with heavy rainfall.

Thunderstorm Wind in JEFFERSON, MONTANA
From 05-SEP-13 18:30:00 to 05-SEP-13 18:30:00 (MST-7)
Location: BOULDER ARPT
Magnitude: 69.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

High winds measuring 69KT (79MPH) tipped a pivot over.

Thunderstorm Wind in HILL, MONTANA
From 05-SEP-13 18:15:00 to 05-SEP-13 18:15:00 (MST-7)
Location: GILDFORD
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

High winds estimated 52KT (60MPH).

Thunderstorm Wind in CASCADE, MONTANA
From 06-SEP-13 16:20:00 to 06-SEP-13 16:20:00 (MST-7)
Location: ARMINGTON
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

High winds estimated 61KT (70MPH) in the Armington Junction area.

Thunderstorm Wind in CASCADE, MONTANA
From 06-SEP-13 16:20:00 to 06-SEP-13 16:20:00 (MST-7)
Location: ARMINGTON
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

High winds estimated 52KT (60MPH).

Thunderstorm Wind in CASCADE, MONTANA
From 06-SEP-13 15:32:00 to 06-SEP-13 15:32:00 (MST-7)
Location: ADEL
Magnitude: 60.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

High winds measuring 60KT (69MPH) at Millegan.

Thunderstorm Wind in TOOLE, MONTANA
From 06-SEP-13 17:26:00 to 06-SEP-13 17:26:00 (MST-7)
Location: SUNBURST ARPT
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

High winds estimated 52KT (60MPH) with tree branches reported down.

Hail in CASCADE, MONTANA
From 07-SEP-13 15:15:00 to 07-SEP-13 15:15:00 (MST-7)
Location: CASCADE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Hail measuring 1.75 inches (golf ball sized) was reported, along with damage to homes and vehicles, 20 mi S of Cascade, MT. Storm lasted about 15 minutes.

Hail in CASCADE, MONTANA
From 08-SEP-13 12:10:00 to 08-SEP-13 12:10:00 (MST-7)
Location: ULM
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail measuring 1.00 inches (quarter sized) was reported 5 mi SSE of Ulm, MT.

Hail in CASCADE, MONTANA
From 08-SEP-13 12:50:00 to 08-SEP-13 12:50:00 (MST-7)
Location: STOCKETT
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail measuring 1.75 inches (golf ball sized) and 35MPH winds were reported 4 mi ESE of Stockett, MT.

Hail in CASCADE, MONTANA
From 08-SEP-13 13:00:00 to 08-SEP-13 13:00:00 (MST-7)
Location: STOCKETT
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Hail measuring up to 2.00 inches (lime sized) was reported in Stockett, MT via a KRTV Facebook report.

Hail in CASCADE, MONTANA
From 08-SEP-13 13:03:00 to 08-SEP-13 13:03:00 (MST-7)
Location: STOCKETT
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail measuring 1.50 inches (ping pong ball sized) was reported 5 mi ESE of Stockett, MT.

Hail in CASCADE, MONTANA
From 06-SEP-13 14:55:00 to 06-SEP-13 14:55:00 (MST-7)
Location: MID CANON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail measuring 1.00 inches (quarter sized) was reported in the Dearborn, MT area.

Hail in FERGUS, MONTANA
From 06-SEP-13 15:35:00 to 06-SEP-13 15:35:00 (MST-7)
Location: SPRING CREEK JCT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail measuring 1.00 inches (quarter sized), along with brief heavy rain, was reported.

Heavy Rain in TOOLE, MONTANA
From 08-SEP-13 16:55:00 to 08-SEP-13 17:55:00 (MST-7)
Location: FERDIG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy rain measuring 0.95 in one hour during the morning with 0.60 more across a couple afternoon hours.

Hail in CASCADE, MONTANA
From 06-SEP-13 15:10:00 to 06-SEP-13 15:10:00 (MST-7)
Location: ADEL
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail measuring 1.75 inches (golf ball sized) and rainfall of .45 inches was reported by Sieben Livestock. Damage to siding of a residential building was also reported.