This is Alex Marienthal with the avalanche forecast for Sunday, December 15th at 7:00 am. This information is sponsored by Polaris and Highline Partners. This forecast does not apply to operating ski areas.
This morning, near Island Park and West Yellowstone have 4-6” of new snow, with 0” in Hyalite and 2-3” everywhere else. Wind has been out of the southwest and west at 10-20 mph with gusts of 30-45 mph. Temperatures are teens to 20s F.
Today temperatures will be in the teens and 20s F and drop to low teens F this afternoon. Wind will be out of the west and northwest at 10-20 mph with gusts to 35 mph. A period of heavy snow is expected this morning, favoring mountains near Bozeman and Big Sky with 5-8”, and 2-3” expected near Cooke City, West Yellowstone and Island Park. Snowfall will taper with light snowfall tonight in some places, and more snow possible tomorrow.
All Regions
Today wind slab avalanches are possible to trigger and could be large enough to bury or injure a person. Moderate to strong wind is drifting new snow into fresh slabs. Yesterday, in the Taylor Fork a snowboarder triggered a wind slab avalanche (obs. and photo), and at Big Sky the ski patrol reported fresh hard slabs that ranged from stubborn to easy to trigger. Heavy snowfall is possible this morning in some areas (Bridgers, Hyalite, Big Sky), so anticipate hazards to increase through the day with fresh slabs easy to trigger.
On many slopes these slabs formed on top of a weak snow surface, and add weight to weak layers of surface hoar and facets that were recently buried up to 12” deep (Blackmore video, Cooke City photo1, Cooke City Photo 2, Taylor Fork surface hoar video). Mark was in Island Park yesterday and described the snowpack as a “sandbox of facets” (video). I went to Saddle Peak in the Bridgers and found facets below a hard slab as well as weak snow on the surface (video, observation).
Carefully evaluate the snowpack for fresh drifts and recently buried weak layers. Cracking across the snow surface or fresh avalanches are clear signs that you could trigger a wind slab. Even without these signs, fresh drifts are wise to avoid, especially in higher consequence terrain.
Today, wind slab avalanches are possible to trigger and the avalanche danger is MODERATE.
Upcoming Avalanche Education and Events
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar
Thursday, Dec 19 and Saturday, Dec 21, Companion Rescue Clinic at REI in Bozeman and History Rock. 6 to 8 pm on Thursday, 10 to 2 pm on Saturday.
Friends of the Avalanche Center: Fall Fundraiser!
We’re still counting on your support and the online Fall Powder Blast fundraiser is 79% of the way to our goal. Please consider making even a small donation HERE or via Venmo