Good Morning. This is Eric Knoff with the Gallatin National Forest Avalanche Advisory issued on Saturday, December 3rd at 7:00 a.m. Today’s advisory is sponsored by Cooke City Motorsports and Gallatin Valley Snowmobile Association in partnership with the Friends of the Avalanche Center. This advisory does not apply to operating skier areas.
Overnight a fast moving storm dropped 1-2 inches in the mountains across the advisory area. At 5 a.m. temperatures range from the single digits to mid-teens F. Winds are blowing 15-25 mph out of the W-SW with stronger gusts recorded around Hyalite and Big Sky. Today, scattered snow showers are possible, but no real accumulation is expected. Temperatures will warm into the upper teens to mid-20s F and winds will continue to blow 15-30 mph out of the W-NW. An active weather pattern moves into the area tonight through Monday. Widespread snow showers develop by Sunday afternoon and significant accumulation is likely by Monday morning.
Bridger Range Northern Gallatin Range
Northern Madison Range
The storm Thursday night was the first real test for a weak and shallow snowpack. The first significant load is often an active time for avalanche activity. Yesterday, natural avalanches were observed in the Bridger Range and Hyalite. The most notable being a large slide on the Apron at Bridger Bowl. Alex also observed a few small slides and got unstable results in stability tests while visiting the Yellowstone Club near Big Sky. These are all prime indicators the snowpack is unstable.
Today, I expect the snowpack to remain sensitive to human triggers. Increasing winds will make wind loaded slopes the primary avalanche concern. With plenty of low density snow available for transport, wind slabs will grow in size and distribution as the day progresses. Pay attention to obvious signs of instability such as cracking-collapsing and avoid steeper terrain where these signs are present.
Today, human triggered avalanches are likely on wind loaded slopes which have a CONSIDERABLE avalanche danger. Non-wind loaded slopes have a MODERATE avalanche danger.
Southern Madison Range Southern Gallatin Range Cooke City
Lionhead area near West Yellowstone
The southern mountains were not favored by Thursday night’s storm. Without new snow, the snowpack is in a state of limbo. The main issue now is the overall integrity of the existing pack. As the snow sits around, it’s getting weaker by the day (video, video). This will be a growing concern as strong winds and heavy snow impact the area Sunday and Monday.
For now, avalanches are unlikely on non-wind loaded slopes. In areas that have received wind loading, it will be possible for skiers or riders to trigger slides. Pay close attention to changing conditions and always be asking – Is the weather contributing to instability? If heavy snow transport it observed, it will best to avoid riding on or under steep terrain.
Today, the avalanche danger is rated MODERATE on wind loaded slopes and LOW on non-wind loaded slopes.
Alex will issue the next advisory tomorrow morning at 7:30 a.m. If you have any snowpack or avalanche observations please drop us a line at mtavalanche@gmail.com or leave a message at 406-587-6984.
BOZEMAN
6 December, Avalanche Awareness, 6-7:30 p.m. at MSU with Backcountry Squatters Ski Club, SUB Procrastinator Theater.
7 December, Avalanche Awareness, 6-7:30 p.m. at REI.
15 December, Avalanche Awareness and Beacon Practice, 6-8 p.m. at Beall Park.
BUTTE
TOMORROW! 1 December, Snowmobiling In and Identifying Avalanche Terrain, 6-7 p.m. at Redline Sports
HELENA
8 December, Avalanche Awareness, 6-7:30 p.m. at The Basecamp.
WEST YELLOWSTONE
15 and 16 December, Snowmobile Introduction to Avalanches w/ Field Day, West Yellowstone Holiday Inn Conference Hotel. More info and sign up HERE.
COOKE CITY
Every Friday and Saturday, Weekly rescue training and snowpack update, Cooke City Chamber of Commerce on Friday 6-7:30 p.m. and field location TBA for Saturday.
BILLINGS
15 December, Snowmobiling In and Identifying Avalanche Terrain, 6-8 p.m., location TBA