The Observation Fire south of Hamilton exploded Tuesday evening and Wednesday, doubling in size to more than 630 acres. Fire information officer Dixie Dies says strong winds led to the fire’s rapid growth.

"When I was talking to our deputy this morning he said, 'you know, I could not believe it. I was standing there and I was talking to the district ranger and we were looking at the fire and saying 'you know, this is looking pretty good'' and then, literally, he turned around and the fire blew up. That's how fast the wind came in and the fire went over the ridge," Dies said.

According to Dies, the direction of the fire’s spread has been up and over the mountain, not toward the valley where there are more people and structures. Still, the complexity of the fire has changed a new management team will arrive shortly.

"There will be a Type 1 team that will come in and probably take over the fire some time Friday. We are expecting winds again today, and probably tomorrow, as well as thunderstorms and lighting."

Already, three smaller fires have been spotted in the Bitterroot National Forest, apparently caused by lightning and about a tenth of an acre in size.

The Ravalli County Commissioners enacted a state of emergency for the county today,  giving law enforcement the ability to evacuate if the need arises.