A severe thunderstorm Monday afternoon passed from south to north through Western Montana, leaving behind broken trees, downed power lines and forest fires.

A majority of Missoula-based broadcast facilities were knocked off the air by power outages, and 60 mph winds took down trees and power lines throughout the Bitterroot Valley.

There were reports of major damage at the Missoula County fairgrounds, where preparations were being made for this weekend's Western Montana Fair.

Meanwhile, 10 forest fires have been reported so far from lightning strikes, according to Joni Lubke of the Bitterroot National Forest. All the fires are about a tenth of an acre in size and crews have responded to five of them.

At the south end of the valley, in the Darby and Sula Ranger District, crews are at a fire 9 miles up Lost Horse Canyon and at a fire in the Lost Trail ski area. Other fires on those ranger districts are in the Benson Creek area, off of Rye Creek; along Martin Creek up the East Fork and in Whisky Gulch off of Robbins Gulch.

On the Stevensville Ranger District, four fires have been reported near Burnt Fork Lake, where a large number of lightning strikes occurred. The other fire is located near Fool Hen Lake. Fire crews are at those fires or are en route.

A Forest Service helicopter is assisting with the Stevensville district fires.