As an upper level low approached the Pacific Northwest coast, a mid-level jet maximum of 40 to 50 knots triggered a line of thunderstorms that moved from eastern Oregon into the Idaho Panhandle.  As this line continued to track east-northeast, they formed a gust front triggering even stronger storms over western Montana that brought strong gusty winds, frequent lightning, heavy rain and damage. The lightning detection network reported over 1500 strikes during the event.

Hail in FLATHEAD, MONTANA
From 29-AUG-13 15:20:00 to 29-AUG-13 15:30:00 (MST-7)
Location: KILA
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter northwest of Kila reported estimated penny sized hail and strong winds estimated at 50 mph that blew off patio furniture from their deck.

Hail in FLATHEAD, MONTANA
From 29-AUG-13 15:30:00 to 29-AUG-13 15:40:00 (MST-7)
Location: KALISPELL
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter northwest of Kalispell reported strong winds with penny size hail.

Thunderstorm Wind in FLATHEAD, MONTANA
From 29-AUG-13 15:50:00 to 29-AUG-13 16:00:00 (MST-7)
Location: COLUMBIA FALLS
Magnitude: 43.00 EG
Property damage: 4.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported strong gusty winds that brought down power lines and trees of unknown size. They also reported pea size hail.

Hail in FLATHEAD, MONTANA
From 29-AUG-13 15:54:00 to 29-AUG-13 15:54:00 (MST-7)
Location: COLUMBIA FALLS
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported nickel size hail southwest of Columbia Falls.

Thunderstorm Wind in FLATHEAD, MONTANA
From 29-AUG-13 16:10:00 to 29-AUG-13 16:40:00 (MST-7)
Location: APGAR
Magnitude: 52.00 EG
Property damage: 8.00K
Crop damage: 0.00K
Reported by: Park/Forest Service

A Glacier National Park official reported several cars damaged from downed trees. They also reported that there were several areas with rocks on the road partially blocking lanes, but no major landslide activity. Approximately 22 miles to the northwest in Polebridge, the RAWS sensor measured a wind gust to 50 mph at 4:50 pm MDT.

Thunderstorm Wind in FLATHEAD, MONTANA
From 29-AUG-13 15:50:00 to 29-AUG-13 16:10:00 (MST-7)
Location: COLUMBIA FALLS
Magnitude: 43.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Newspaper

The Daily Inter Lake newspaper reported that a tree had fallen on a home on Kokanee Bend two miles southwest of Columbia Falls. The law enforcement scanner traffic indicated that the tree had cut the home in half trapping the people inside. They were uninjured and were eventually able to get out of the house.

Thunderstorm Wind in FLATHEAD, MONTANA
From 29-AUG-13 15:32:00 to 29-AUG-13 15:55:00 (MST-7)
Location: (FCA)KALISPELL INTL
Magnitude: 48.00 MG
Property damage: 3.50K
Crop damage: 0.00K
Reported by: ASOS

The weather sensor at the Kalispell International airport reported a gust to 55 mph,  and heavy rain with reduced visibilities as low as one mile for at least 19 minutes. It reported 0.27 of rainfall in 23 minutes from 4:32 to 4:55 pm MDT. As the gust front moved through the Kalispell area, there were reports of a dust storm that brought visibilities down to near zero for several minutes before the rain began. The dust cloud moved through an open door of the Glacier High School setting off fire alarms and filling the school with dust. The school's custodial staff had to spend the night removing and cleaning the dust out. The strong wind caused large trees to fall, knocking down power lines and blocking roads. The power company reported approximately 2,500 people without power for a time that evening.