Firefighters Chris Wetzel, left, and Mitch Sprague, from Lafayette Fire, clear brush from the Moraine Park Visitor Center on Sunday. The Fern Lake fire
Firefighters Chris Wetzel, left, and Mitch Sprague, from Lafayette Fire, clear brush from the Moraine Park Visitor Center on Sunday. The Fern Lake fire forced the evacuation of hundreds of homes. (Photos by Helen H. Richardson, The Denver Post)

ESTES PARK —High winds were expected to make it perilous overnight in the Marys Lake community southwest of Estes Park, as the Fern Lake fire blazes a few miles away.

Winds could gust up to 70 mph until about 3 a.m., and a critical "red flag" fire danger warning remains in effect until 6 a.m. Monday.

After 250 firefighters tried to hem in the fire Sunday, 150 were assigned to the fire overnight, mainly in home-protection mode, Sheriff Justin Smith told residents at a town meeting Sunday night.

He said he hoped the planning and concern were in vain, but he said residents should pack their most valuable belongings in advance and flee if they get the call.

"If it was me, and I had livestock, I'd have them out and ready to go," Smith said.

Photos: Fern Lake fire

At 9 p.m., sustained winds were between 30 mph and 40 mph in the area.

Firefighting helicopters and air tankers were grounded Sunday afternoon because of winds, as ground crews shored up the perimeter. The Fern Lake fire started from and illegal campfire Oct. 9 in remote terrain and has spread to 3,580 acres, but as of Sunday evening, only a privately owned cabin has been lost. No firefighters have been injured in the steep, rough terrain of Rocky Mountain National Park.

If wind gusts push the fire into the treetops — as they did late Friday night and early Saturday morning — residents connected to about 1,100 phone lines could be forced to flee.

Authorities were concerned about the Marys Lake area, about 4 miles southwest of Estes Park.

"I don't really want to kick anybody out of their homes if I don't have to," Smith told the full house at the Estes Park meeting.

Pre-evacuation notices have been sent to phone lines west of Marys Lake Road, from Moraine Avenue and Rock Ridge Road South to Colorado 7 and Fish Creek Road.

He said once the wind dies down, authorities would have a much better idea of when existing evacuees would be able to go home.

The fire remained at 20 percent containment.

Residents of Estes Park were not on alert to evacuate Sunday night, however. The business district of Estes Park was hazy and smelled strongly of smoke Sunday morning.

"You expect it to be hot and smoky in the summer, but in December?" said Larry Airgood, manager of the Wynbrier Ltd., a wildlife gallery in Estes Park.

He speculated that wildlife in the fire zone would be OK unless the fire covered a great distance in a short time overnight.

"The fire has been burning for a while, so they've already done whatever they're going to do," Airgood said.

As with Colorado wildfires last summer, people with breathing problems should stay indoors and avoid exerting themselves, fire-information officer Traci Weaver said at the community meeting.

Early Saturday, wind gusts of up to 75 mph doubled the size of the blaze and pushed it 3 miles to the east in 35 minutes. At about 1 a.m. Saturday, residents of 583 homes along the Colorado 66 corridor were forced to leave and remained evacuated Sunday.

About 250 firefighters were on the scene Sunday, and "more are on the way," the sheriff said.

A Type 1 team of federally trained and funded firefighters took command of the battle from local authorities Sunday evening.

The fire is burning winter-dry grasses and dense lodgepole pines, but it primarily has lingered by consuming beetle-killed trees in abnormally dry conditions.

Windy conditions return Monday with gusts up to 45 mph. Breezy conditions could linger in the area until Wednesday, according to the National Weather Service.

The overnight fire-danger warning included areas above 6,000 feet in elevation in central and southeast Park County, Boulder and Jefferson counties, and west Douglas County.

Joey Bunch: 303-954-1174, jbunch@denverpost.com or twitter.com/joeybunch