Plunging humidity fuels Northwest Montana fires

Even with calmer winds, fire activity picked up on the Brush Creek Fire and other Northwest Montana fires as humidities plunged late Tuesday afternoon.

Firefighters continued to struggle with spot fires on the northern perimeter of the Brush Creek Fire, located about 23 miles southwest of Whitefish.

The late afternoon size-up showed the fire had gained only about 5 acres, covering a total of 26,425 acres. But those numbers could change significantly by this morning because of the bone-dry burning conditions and troublesome spot fires that have popped up beyond northern containment lines.

"Late in the day, humidities have dropped down to 9 percent. When it's that dry, everything burns easily," said Mary Huels, Brush Creek fire information officer. "It's not windy, but they are worried about plume-driven fire behavior. When it gets this dry, the fire can basically make its own wind."

Fire managers relied heavily on aircraft to patrol for and put out spot fires. Helicopters and single-engine air tankers made concentrated drops on the northwest perimeter, where the fire made a wind-driven run on Sunday near Dunsire Point.

Fire managers have been waiting for opportunities to do burnout operations to reinforce vulnerable sections of containment lines. Those plans were again canceled Tuesday because of risky conditions.

Firefighters made progress on the southern perimeter, working 300 feet into the black in some areas to extinguish hot spots.

Infrared mapping from a patrol flight early Tuesday morning sized the Chippy Creek Fire at 77,173 acres.

While there was active burning Tuesday, with humidities as low as 16 percent, the fire did not make any significant runs, said Dixie Dies, fire information officer.

Firefighters have been preparing areas ahead of the northeast and northwest fire perimeters for burnout operations, possibly to be carried out today.

Fire bosses on the Chippy Creek Fire and other project fires in Northwest Montana are anticipating a cold front to arrive Thursday, with potential for high winds ahead of thunderstorms.

"We're trying to take care of things and get ready for that," Dies said.

While high winds were not an issue elsewhere in the region, they were on the Skyland Fire south of Marias Pass Tuesday afternoon.

But even with gusting winds, burning activity was within most containment lines and the fire did not make any significant runs, said fire information officer Mike Heilman.

Crews are moving hoselines from creek to creek, mopping up blackened areas on the northern perimeter. Fireline rehabilitation work is underway on the east and west "bookends" of the 40,548-acre fire, which stretches more than 19 miles long.

Fireline explosives were used to blast a line aimed at preventing the fire from spreading south toward a Forest Service guard station. The fire is considered 60 percent contained.

"We're starting to ramp down people," Heilman said, with personnel on the fire down from a high of more than 1,000 to about 800 on Tuesday. "I imagine that will continue over the next few days."

Meanwhile, initial attack firefighters have been trying to corral a new fire on the east side of the Swan Mountain Range, about two miles northeast of Strawberry Lake.

The lightning-triggered Wounded Creek Fire emerged Monday afternoon, and by late Tuesday it was estimated at 17 acres. A 20-person crew was working the fire, along with helicopters making water drops.

Reporter Jim Mann may be reached at 758-4407 or by e-mail at jmann@dailyinterlake.com