A cluster of thunderstorms developed at 3 pm MDT over Lemhi county and was associated with very frequent lightning strikes. This cluster of thunderstorms developed into a line and brought strong damaging winds to the Bitterroot and Missoula valleys. Numerous power lines were knocked down as a line of 60 mph winds push through the Bitterroot valley. As the thunderstorms approached Missoula, a macroburst developed and brought 74 mph wind gusts to the city of Missoula. Many power lines and trees were brought down and caused power outages for days in some areas.

Thunderstorm Wind in LAKE, MONTANA
From 10-AUG-15 19:17:00 to 10-AUG-15 20:00:00 (MST-7)
Location: ST IGNATIUS
Magnitude: 43.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Power lines and trees were downed by the wind. One of the trees that was knocked over was 18 inches in diameter.

Thunderstorm Wind in MISSOULA, MONTANA
From 10-AUG-15 18:22:00 to 10-AUG-15 19:15:00 (MST-7)
Location: (MSO)MISSOULA INTL A
Magnitude: 64.00 MG
Property damage: 1.00M
Crop damage: 0.00K
Reported by: ASOS

A macroburst brought damaging winds to the city of Missoula. A 74 mph wind gust was measured at the Missoula airport, but a majority of the damage occurred towards the
South Hills area. Major power lines and large trees were knocked down, and some residents were without power for four days. A local power company reported that several power poles, rated at 80 mph, were snapped in half. Over a million dollars in damages is estimated for this event.

Thunderstorm Wind in RAVALLI, MONTANA
From 10-AUG-15 17:30:00 to 10-AUG-15 18:00:00 (MST-7)
Location: STEVENSVILLE
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A fence with 5 x 5 inch posts was blown down. Wind estimates near 60 mph.

Thunderstorm Wind in MISSOULA, MONTANA
From 10-AUG-15 18:06:00 to 10-AUG-15 18:30:00 (MST-7)
Location: LOLO
Magnitude: 43.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: NWS Employee

NWS employee reported a power outage, and tree limbs 5 to 6 inches in diameter broke off. Estimated winds of 50 mph.

Thunderstorm Wind in MISSOULA, MONTANA
From 10-AUG-15 18:44:00 to 10-AUG-15 19:45:00 (MST-7)
Location: PILTZVILLE
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Multiple downed trees in Turah. Also the highway sign for Bonner was broken off by the wind. Wind speeds of 60 mph estimated.

Thunderstorm Wind in MINERAL, MONTANA
From 11-AUG-15 18:25:00 to 11-AUG-15 18:25:00 (MST-7)
Location: BORAX
Magnitude: 50.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A strong thunderstorm unleashed a small microburst that caused hundreds of trees to either snap in half or blow over at the Denna Mora Rest Area on Interstate 90 east of Lookout Pass.  Two large fir and spruce trees with diameters up to 3 feet wide fell onto the eastbound lanes just to the northwest of the rest area obstructing the road at night. Approximately an hour later around 10 pm MDT, several vehicles hit the trees causing car damage, injuries and one fatality. A 21 year old male died after his vehicle collided with the topmost of the crisscrossed trees.

Thunderstorm Wind in RAVALLI, MONTANA
From 10-AUG-15 17:00:00 to 10-AUG-15 17:30:00 (MST-7)
Location: CONNER
Magnitude: 51.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter estimated 59 mph wind gust. A person from the public on Facebook estimated wind gusts were over 65 mph in Darby.