This is Ian Hoyer with pre-season information from the Gallatin National Forest Avalanche Center on Friday, November 29th at 7:30 am. This information is sponsored by Highline Partners and Klim. You can donate to The Friends of the GNFAC’s Fall Fundraiser HERE.
We will begin daily forecasts with danger ratings tomorrow.
No snow has accumulated since our last update on Wednesday. Winds have been out of the west at 10-20 mph with gusts of 15-35 mph. Temperatures this morning are single digits to teens F. Cloudy skies this morning will clear during the day with high temperatures reaching the teens and 20s F. Wind will be 10-20 mph out of the west and southwest. No snowfall is expected.
All Regions
The primary concern today is avalanches breaking within or beneath wind drifts. These could be either wind slab or persistent slab avalanches.
Any steep slope with a hard slab of drifted snow holds the potential for a wind slab avalanche. The more recently the wind drift formed, the more likely it is to be unstable. Stay alert for visual signs of wind drifting or a change in the feel of the snow under your feet or machine. If you encounter a punchy drift, stop and assess how well it’s bonded. Cracks shooting out in front of you are a clear sign that you’ve found an unstable drift and should avoid steep slopes.
Persistent slab avalanches breaking on weak faceted snow are not yet a widespread hazard, but these slides would break deeper, wider, and potentially further above you, so they’re definitely worth putting some thought into. Big Sky Ski Patrol continues to trigger substantial avalanches while doing avalanche mitigation work with explosives. Some are breaking just within wind drifts and some are breaking deeper. Yesterday, they triggered a slide with a 5-6 ft deep crown (photo). Unfortunately, the snowpack is starting to weaken in many areas (Lionhead video, Blackmore video, Cabin Creek video). For now, this weakening hasn’t progressed too far and is only a real concern if the weak snow is capped by a slab of wind drifted snow. If you find stiff snow at the surface, quickly dig down to look for weak layers beneath.
Keep in mind that a slide of any size would have big consequences right now, with lots of rocks and other obstacles still exposed.
Your observations are incredibly valuable. Contribute to our community’s knowledge by submitting your observations, and look through our observation page for additional information before your next backcountry adventure.
Upcoming Avalanche Education and Events
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar
Monday, December 2, 6:30 p.m. MAP community partnership night and 1-hr Avalanche Awareness, at MAP Brewing
Tuesday, December 10, 9 a.m.-3 p.m., West Yellowstone Avalanche Fundamentals: Motorized Guide Cert Course, Pre-registration required.
For an intro class with a field day, Register for our Avalanche Fundamentals course.
Friends of the Avalanche Center: Fall Fundraiser!
We’re still counting on your support and the online Fall Powder Blast fundraiser is 77% of the way to our goal. Please consider making even a small donation HERE or via Venmo.
Bridger Bowl has backcountry conditions and there are no ski patrol services. Please steer clear of snowmaking equipment, chairlifts and snowmobiles, and respect posted signage, while they set up for the season.