The National Weather Service issued a winter weather advisory for the Flathead and Mission valleys and West Glacier region on Friday morning, after accumulating snow in valleys and mountains caused slick road conditions and car accidents as skiers and snowboarders rushed up to Whitefish Mountain Resort (WMR) for a 5-inch powder day.A multi-vehicle accident occurred at 7 a.m. on Big Mountain Road, Flathead County Sheriff Brian Heino said, causing backed-up traffic, which delayed the mountain’s opening.“It sounds like traffic was backed up to Highway 40 at one point,” Heino said.“That was a pretty unique case for us with the crashes on the mountain early this morning,” WMR Public Relations Manager Maren McKay said. “We typically don’t see that level of traffic.”A winter storm watch remains in effect from Saturday afternoon until Sunday morning, and the National Weather Service reported one to three inches of new snow in the Flathead Valley and three to 10 inches elsewhere. Forecasters expect a total of six to eight inches in the valley and six to 12 inches elsewhere, with up to 16 inches in the high country. Areas to watch include Bad Rock Canyon, Essex, U.S. Highway 83 to Bigfork to Swan Lake, Marias Pass, Polebridge, Flathead Lake, Polson and the Flathead and Mission valleys.An arctic airmass is expected to “slide over” central Montana with arctic air expected around Glacier National Park and as far west as Kalispell by Saturday morning. Temperatures are expected to drop 30 degrees below zero in some areas of Northwest Montana, with temperatures in Kalispell dropping to negative 8 on Monday night.Additionally, the Flathead Avalanche Center issued a backcountry avalanche warning in the Swan and Flathead mountain ranges and Lake McDonald and Marias Pass areas of Glacier National Park on Friday morning.Avalanche forecasters rated the Whitefish Range as “considerable” on the avalanche danger scale on Friday with six to eight inches of snow expected through Saturday. The Flathead and Swan ranges were rated as “high” on Friday morning.The Flathead Range and Glacier Park are expected to see 13 to 18 inches through Saturday while the Swan Range is expected to see 20 to 23 inches.“The forecast region has seen a spate of large and very large natural, human and remotely triggered avalanches in the past week,” Forecaster Clancy Nelson wrote in the Feb. 5 forecast discussion. “People have reported near misses and at least one person was caught, carried and slightly injured. These slides have occurred nearly every day, not just during storms … This hazard is growing even more serious as a potent storm lashes our area.”For more weather information, visit www.weather.gov/mso/. For the latest avalanche forecast, visit www.flatheadavalanche.org. Email Stay Connected with the Daily Roundup. Sign up for our newsletter and get the best of the Beacon delivered every day to your inbox.