Weather experts are predicting an extreme snowfall event for northwest Montana on Sunday and Monday unlike any the region has seen in decades.

Nearly 3 feet of new snow is forecast to accumulate in the Flathead Valley by Tuesday morning as a potent plume of moisture collides with an arctic air mass moving across the region.

Kalispell, Whitefish, Bigfork, Eureka and Libby could get buried with 24 to 30 inches of snow by Tuesday morning, the National Weather Service warns, while West Glacier and Polebridge could see between 36 and 50 inches of accumulation.

“This is potentially a huge storm. Something we haven’t seen in decades,” said meteorologist Trent Smith with the National Weather Service in Missoula.

Many parts of the Flathead Valley already received about 14 inches of new snow on Saturday, “but things really start to get interesting come Sunday afternoon through Monday,” Smith warned.

“Come Sunday night this arctic air will be spilling into northwest Montana and really enhance the precipitation over Glacier National Park,” he said.

Snowfall rates could be between 2 to 4 inches per hour, while gusting eastern winds could cause localized blizzard conditions, especially near Bad Rock canyon and Columbia Falls. Roof damage and roof avalanches are possible, Smith warned.

“There are going to be times that snow plows are not going to be able to keep up with the amount of snow falling,” Smith said.

“This is just a phenomenal amount of snow. Travel is going to be extremely impacted,” Smith added. “We’re talking about feet of snow. I can’t reiterate that this is a huge, huge system.”

Temperatures will top out around 20 on Monday with lows in the single digits Monday night. The snowstorm should clear out by Tuesday night.