U.S. 2 along the southern boundary of Glacier National Park was closed at 3 p.m. Thursday as the Sheep Fire continued to push northeast from Flathead National Forest, south of Essex.

The closure is between mile markers 178 and 185 — at the Halfway Motel on the west side and Bear Creek on the east side.

Later Thursday afternoon, highway officials began turning away motorists at West Glacier and East Glacier Park. Only people who live in that area or have lodging reservations are being allowed to travel between those points on U.S. 2.

Flathead County emergency information officer Jennifer Rankosky says the highway and railway were closed after embers began falling on the roadway. The 232-acre fire was a half-mile from the highway Thursday night.

The BNSF Railway line through the Middle Fork corridor also was closed Thursday.

There is no evacuation of the Essex area underway, although the area was put on a pre-evacuation notice Wednesday.

The fire has remained about two miles south of Essex, and fire information officer Greg Dinetto said an evacuation wasn’t contingent on the fire coming within a specific distance of the community.

“The trigger point that has been identified, rather than a hard line, is essentially a call by the operations folks observing the fire and the weather conditions,” he said. “When they see what they consider uncontrollable fire behavior and movement, and weather that could move the fire toward Essex, that’s when they would make a decision on-site for evacuation.”

Dinetto said fire behavior analysts expected the fire would reach U.S. 2 by Friday morning.

A red flag warning is in effect today from 11 a.m. to 9 p.m. as a cold front is forecast to bring high winds — gusting up to 40 miles per hour on the ridgetops — into the area.

“The fire behavior folks, one of their concerns is if we get a thermal belt — essentially an inversion with the smoke and cooler air sitting low — and that thermal belt at 5,000 feet [with] much of the fire above that,” Dinetto said. “Once you get above that inversion layer, it’s going to be staying warm, dry and breezy.”

Officials with Glacier National Park and the fire management team are preparing for the possibility of the Sheep Fire jumping across the highway and the Middle Fork Flathead River and into the park.

“They’re starting to look at the park side, do some assessment of what values are at risk over there,” he said.

Kimberly Woods, a spokeswoman for Amtrak, said in an email Thursday night that service for the eastbound Empire Builder train is canceled between Sandpoint and Cut Bank, with no alternative transportation provided.

Westbound Amtrak trains will stop at Shelby. Bus transportation will be provided to Spokane.

BNSF Railway spokesman Matt Jones said 30 to 35 freight trains a day usually travel the Middle Fork Corridor.

With U.S. 2 closed, the nearest east-west roadway is Glacier Park’s Going-to-the-Sun Road. The nearest roadway that trucks are allowed to travel on is more than 100 miles south on Montana 200.

Dinetto said that no crews were providing ground attack on the Sheep Fire since they were pulled off Wednesday due to unsafe conditions.

Three smokejumpers were on the 3-acre Spruce Fire, using initial attack to try to put down the blaze before it grows significantly.

Three helicopters worked the fires on Thursday using a newly arrived mobile fire retardant plant to perform drops on the flame front.

“We set it up near the fire and we’re able to mix our own retardant,” Dinetto said. “Using that for bucket drops from helicopters is more effective than straight water.”

The steep, narrow topography in the area makes retardant drops from choppers more efficient than single-engine planes, he explained.

Among the 253 personnel present on Thursday, four hand crews were deployed, some of them helping with structure assessment and protection in Essex, where eight fire engines are stationed.

There are 200 threatened structures in the area, according to fire officials, which include homes, vacation cabins and the Izaak Walton Inn. The privately owned lodge was built in 1939 and is an attraction for cross-country skiers and visitors to Glacier Park.

Beyond today’s high winds, the weather is predicted to bring lower temperatures including snow as low as 6,000 feet.

Reporter Samuel Wilson can be reached at 758-4407 or by email at swilson@dailyinterlake.com.