GNFAC Avalanche Forecast for Mon Dec 11, 2023

Not the Current Forecast

Good morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Forecast on Monday, December 11th at 7:00 a.m. This information is sponsored by Highline Partners and Gallatin County Sheriff Search and Rescue. This forecast does not apply to operating ski areas.

Bridger Bowl is closed through Thursday. Uphill travel is permitted. Backcountry conditions exist with no avalanche mitigation or ski patrol services. Call 911 for rescue.

Mountain Weather

The mountains received 1-3” of snow since yesterday morning. Wind out of the west decreased to 5-15 mph after gusting to 35 mph yesterday. This morning temperatures are teens to 20s F, and today will reach mid-20s to 30 F. Wind will be west-northwest at 5-15 mph. Light snow showers might drop 1-2” today before high pressure brings mostly clear skies for the rest of the week.

Snowpack and Avalanche Discussion

All Regions

The mountains throughout the forecast area have dangerous avalanche conditions due to 1-2 feet of snow over the last week falling on a weak snowpack (photo). Human-triggered avalanches are likely today. Yesterday Doug and I went to Beehive Basin and easily got the snowpack to collapse when breaking trail, and we saw a poor snowpack structure similar to elsewhere in the forecast area (video, photo).

Over the weekend we got reports of human triggered avalanches, natural avalanches and widespread collapsing and whumphing of the snowpack, showing the current high potential to trigger an avalanche. Notable recent signs of a dangerous snowpack include (but not limited to):

  • On Saturday a skier triggered and was not caught in an avalanche at Bridger Bowl in terrain that is currently the backcountry (photo).
  • Riders remotely triggered avalanches in Tepee Basin (photo).
  • Natural avalanches were reported in Beehive Basin (photos), Taylor Fork (photos), Cooke City (photo) and on Elephant Mtn. in Hyalite (photo).
  • Skiers, riders and ice climbers had large collapses of the snowpack near West Yellowstone (photos), Hyalite (observation), Cooke City (observation), the Bridger Range (observation), Big Sky (observation) and the southern Madison Range (observation).
  • Find more info in our field videos from the last week from Beehive, Bridger, Hyalite, Island Park, Cooke City and Lionhead (videos), and browse the many recent observations on our website.

Today a person can easily trigger an avalanche on steep slopes and terrain connected to steep slopes. Slopes that did not have snow on the ground prior to last week have better stability, but to identify these areas you must be diligent with snowpack assessment, and other early season hazards are more prevalent due to a shallower snowpack (rocks, logs, etc.). The best plan is to avoid travel on and underneath slopes steeper than 30 degrees. Additionally, recent strong winds drifted snow into thicker slabs, so wind-loaded slopes are especially dangerous (photo).

Throughout the forecast area, human triggered avalanches are likely and the avalanche danger is CONSIDERABLE.

If you venture out, please fill an observation form. It does not need to be technical. Did you see any avalanches? How much snow is on the ground? Was the wind moving snow? Simple observations are incredibly valuable. You can also contact us via email (, phone (406-587-6984), or Instagram (#gnfacobs).

Upcoming Avalanche Education and Events

Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.

Tuesday, December 12th, 9:00 a.m. to 3:00 p.m., West Yellowstone Motorized Avalanche Fundamentals, Pre-registration and more information HERE.

Thursday, December 14th, 6:30 p.m., Community Partnership Series @ MAP Brewing, featuring “RUN” with Wiley Miller, and Q&A with GNFAC forecaster Alex Marienthal

We offer Avalanche Fundamentals with Field Session courses targeted towards non-motorized users in December and January and one geared towards motorized users in January. Sign up early before they fill up.

Loss in the Outdoors, is a support group for those who have been affected by grief and loss related to outdoor pursuits. Check out the link for more information.

The Last Word

Watch this video from Dr. Karl Birkeland (former director of the National Avalanche Center, now retired with more time to do large stability tests) performing a Rutschblock Test and showing how easy it is for a person to trigger an avalanche on our current snowpack.

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