American Fork fire

The American Fork fire burning in the Crazy Mountains shown on July 26.

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A fire in the Crazy Mountains forced a pre-evacuation notice Wednesday evening for homes on Shields River Road as the blaze burns through dry and dense fuels on rough terrain.

The American Fork fire, about 24 miles southwest of Harlowtown, had burned more than 9,500 acres as of Thursday around noon and was about 10% contained, according to InciWeb, a wildfire information service.

An update Thursday morning said winds pushed the fire west into the Shields River drainage, prompting the pre-evacuation notice. The Custer Gallatin National Forest on Thursday did not immediately provide information about how many structures are threatened by the advancing fire.

Cooler and more humid conditions Wednesday and Thursday slowed the fire’s advance, said Brook Smith, public information officer for the Southern Area Gulf Team responding to the American Fork fire.

Some showers and thunderstorms were predicted in the area for Thursday afternoon into the evening, but the chances of rain dip Friday and Saturday as winds are forecast to bring more humidity to the area, said Jim Brusda, lead meteorologists for the National Weather Service in Great Falls.

But near record-high temperatures combined with intense flames have dried dead trees and grasses in the area, creating dangerous conditions for digging handlines to slow fire growth.

“The rain is not going to stop the fire, it’s just not,” Smith said. “It will lower fire activity and allow firefighters to get in closer and put in a handline.”

Conditions in the past week were such that a stray ember landing in fine fuels — like dry grasses or pine needles — had a 90% chance of stating a new fire, Smith said.

“If you’ve got standing dead trees, they’re throwing embers, and that’s out ahead of the fire crews,” he said. “The embers are going down below them, they could have fire race back up to them.”

The heat from the fire — which is burning in timber through the canopy and midstory of the forest — is drying fuels before the fire burns through the area, negating the effectiveness of digging handlines in the forest floor to direct the spread of the fire to naturally fire-resistant areas, like granite bluffs or creek drainages, Smith said.

“The conditions are rough, the terrain is rough, the fuel is dry and there’s a lot of fuel,” Smith said.

The steep terrain in the area also makes it harder for firefighters to get into areas where handlines could be effective — Smith said most of the work fighting the American Fork fire has been done by people, not equipment.

Almost 200 people are working to fight the fire, including crews, engines, dozers, a water tender, a masticator and an excavator, according to InciWeb. The Montana Department of Natural Resources and Conservation, Cascade County and Meagher County are also supporting suppression efforts.

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Bret Hauff is the Chronicle’s city editor. He can be reached at bhauff@dailychronicle.com or {span}406-582-2647.{/span}

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