The National Weather Service is expecting between two and three feet of new snow to fall on the mountain passes between Friday night and next Tuesday and from four to six inches in the Missoula valley.

Meteorologist Marty Whitmore described the patterns setting up over the weekend into the first part of next week as a major snow event.

“We’ve got cold air moving in from the east reinforcing the cold air mass that’s already here, and at the same time, above that we have a really moist westerly flow which will be pushed way up in the atmosphere and that’s a great set-up to produce snow,” said Whitmore. “The mountains are really going to get hit pretty hard, but there is enough warmth in that system so that the valleys won’t get too much snow to start with.”

Whitmore said the valleys will receive a few inches into Saturday, with more at the start of next week.

“Probably the best event for us in the valleys will be Sunday night into Monday,” he said. “Monday morning’s commute will be the most problematic. The valleys will probably see from four to six inches or more here in Missoula from Sunday afternoon to Monday afternoon. The mountains, meanwhile, could see from one to two feet of new snow. Overall, they could se up to three feet of snow in the Bitterroot Mountains pretty easily.”

Whitmore said Lolo and Lost Trail passes will receive the most snow from this event.”

Whitmore said the basins in western Montana are already near 100 percent of normal moisture, but the winter season continues through March and into April.

He said county officials will be watching the snow levels closely to determine if there is a possibility of low level flooding with the spring runoff.