The work was aimed at creating a backfire that would remove 2,000 acres of fuel from the path of the approaching forest fire.
``Tonight, right now what you see as green, will be gone,'' said Clinton Northway, the burnout supervisor.
Even though small backfires the night before had turned the fire, officials were concerned that the blaze could make another run because humidity was extremely low and wind was expected to pick up. The blaze had grown to an estimated 12,100 acres by Tuesday morning.
``This is going to be a complex day, a busy day and a critical day,'' said Chip Houde, operations specialist with the fire incident command team.
While firefighters on the ground started the backfire, big water bombers skimmed across scenic Lake McDonald in the park, filling their tanks with water to dump on trees near evacuated homes and business to make sure the deliberate flames didn't turn on the town.
Crews also planned to use helicopters to drop small incendiaries, so-called ``pingpong balls of flame.''
``It's going to be a pretty chaotic air show,'' said Tom Kempton, a fire information officer.
Sirens screamed Monday evening, warning residents, tourists and remaining National Park Service personnel at park headquarters to evacuate, mostly because the fire was threatening to block U.S. Highway 2, a main escape route.
The fire made a run late Monday, prompting a national fire control team to order a series of small burnouts that succeeded in turning the main blaze to the north, away from developed areas.
``The fire was burning down toward the Middle Fork between two ridges, so we set the backfire up the drainage, and it turned the column ... bent it back,'' fire information officer Andy Williams said Tuesday. ``It was basically like pulling on somebody's hair to stop them from going forward.''
The Flathead County disaster emergency office said Tuesday about 500 people had left and around 60 stayed to protect their homes. Thousands of tourists already had left other parts of the park.
Flathead County Sheriff Jim Dupont said the evacuation order affected more than 400 homes and businesses in the two villages and the surrounding area. It was called mandatory, but Dupont said authorities did not force people to leave.
``We make it very clear that staying is at your risk and when the fire is knocking at your porch, we may not be there to rescue you,'' he said.
The fire threatening West Glacier and Apgar Village was one of three in and around the national park.
An even larger blaze had burned 19,667 acres in the northwest corner of Glacier, just six miles south of the Canadian border, and firefighters there were changing strategies. That fire destroyed six dwellings and 19 outbuildings, and still threatened about 100 other homes and cabins. A third wildfire had burned 16,500 acres inside the park in a remote area north of Going-to-the-Sun Road.
Fires also were active Monday in Arizona, California, Colorado, Idaho, New Mexico, Oklahoma, Oregon, South Dakota, Utah, Washington and Wyoming, the National Interagency Fire Center reported.
