Travel will become difficult to impossible across Northwest Montana this week as a significant and potentially dangerous arctic outbreak sweeps across the region.

The National Weather Service in Missoula warned Monday that the winter punch will clock the Flathead Valley with heavy snowfall, gusty winds and the coldest temperatures of the season.

The surge began Tuesday as snow developed and Flathead residents were expected to be shoveling about 4 inches of new accumulation by Wednesday.

Mountain locations, such as Marias Pass on U.S. 2 south of Glacier National Park, could get walloped with 2 to 3 feet of fresh powder. Snowfall projections are similar for the summit of Big Mountain and the ski slopes at Whitefish Mountain Resort.

“We’re expecting a lot of heavy snowfall,” said Jean Kitsmiller, a meteorologist with the National Weather Service.

Frigid temperatures arrive Wednesday as a cold front sags out of Canada and spills into Montana. Snow will accompany the arctic outbreak, as well, with a couple more inches possible in the Flathead Valley.

“We’ll see a rapid temperature drop and strong northeast winds,” Kitsmiller said.

Wednesday night into Thursday, the arctic air moves deeper into Montana and further enhances snowfall with an additional 3-6 inches possible in Northwest Montana valleys.

“There could be locations that receive higher or lower amounts depending on the surface low track,” the National Weather Service warned in its Monday forecast. “A few of the deterministic models suggest as much as a foot of snow. 

“This could be a high impact event with blowing and drifting snow, especially in the gaps and also surrounding Flathead Lake, and bitterly cold temperatures. This could be a situation where roads could become impassable.”

Extreme lows of minus 20 are likely Thursday night from Eureka south into the Flathead Valley. The low Friday night could approach minus 30 in some areas. 

The frigid cold will be a big change for Kalispell, where temperatures did not dip below zero in November or December.

Yet another round of snow is on deck for next weekend, while low temperatures hang below zero.