This is Ian Hoyer with the avalanche forecast for Saturday, February 15th, at 7:00 a.m. sponsored by Spark R&D and Highline Partners. This forecast does not apply to operating ski areas.
Snowfall started yesterday afternoon and ramped up overnight, with:
8-17” (0.6-0.9” Snow Water Equivalent) near Big Sky
5-7” (0.5-0.7” SWE) near Bozeman
3-4” (0.2-0.3” SWE) near West Yellowstone, Island Park and Cooke City
Winds are 10-15 mph out of the west and northwest, with 20-30 mph gusts. Temperatures are in the teens F.
Snowfall is wrapping up this morning. Winds will remain light out of the northwest and west. The sun may pop out from behind the clouds in places today, but it’ll generally stay cloudy before snowfall starts up again tonight. By tomorrow morning expect 2-4” around Bozeman and 1-3” across the rest of the advisory area. It’ll keep snowing through tomorrow and into Monday.
With new snow overnight, Wind slab avalanches are the primary concern today. Be on alert in places where you find a lot of new snow. Remote weather stations indicate that the deepest snow (in localized areas around Big Sky) is low density (~5%) and I don’t expect it to form cohesive slabs and avalanche by itself - but even a little wind effect could tip the scales and make it reactive and quite dangerous. Without wind, in the deeper areas, watch for Dry Loose avalanches (sluffs) that could be fairly sizable in steep terrain.
Riders triggered thin Wind Slabs up Storm Castle Creek yesterday (observation) and there were quite a few small Wind Slabs triggered on Thursday (N. Bridger’s observation, main fork of Hyalite observation, Mt. Blackmore observation). New snow could mask signs of these older drifts as well as pile up a load on top of them and keep them reactive.
Watch for areas of wind drifted snow and signs that the drifts are unstable (chiefly recent avalanches or cracking). Assess how well wind slabs have bonded to the old snow before getting onto steep slopes.
The avalanche danger is MODERATE today.
Snowfall totals are not very impressive around West Yellowstone, Island Park and Cooke City and there hasn’t been a ton of wind. As with further north, freshly formed Wind Slabs are the primary concern, but they will be less widespread and not as thick. Look out both for thin fresh drifts and somewhat thicker older drifts that formed during the high winds mid-week.
Persistent Slab avalanches are the wild card in these areas. There hasn’t been a ton of activity on the weak layer that formed towards the end of January, but there has been some (Lionhead photo, Cooke City photo, Taylor Fork video). These slides are most likely to be triggered on windloaded slopes, where slabs are more cohesive and thicker. If you do trigger one of these slides it’ll break deeper, wider and be more dangerous.
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
February 18, 3-4 p.m. Whumpfs and anticracks: the science and mechanics of snow slab avalanches. A free advanced snow science presentation by a visiting professor from Germany at Montana State University in Roberts Hall, Room 101.
February 20, 4-7 p.m. Beacon BBQ at Uphill Pursuits in Bozeman. Come try out different brands of avalanche transceivers (or practice with your own!) with coaching from Friends of GNFAC instructors and free hotdogs.
February 28 - March 2, Bozeman Splitfest 2025 - Celebrate all things Bozeman backcountry and raise funds for GNFAC. Enjoy demos, clinics, free food and beer from MAP. Connect with fellow outdoor enthusiasts and soak up the winter stoke.
Every weekend in Cooke City: Friday at The Antlers at 7 p.m., Free Avalanche Awareness and Current Conditions talk, and Saturday from 10 a.m.-2 p.m. at Round Lake Warming Hut, Free Rescue Practice.