GNFAC Avalanche Forecast for Sun Dec 26, 2021

Not the Current Forecast

Good morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Forecast on Sunday, December 26th at 7:00 a.m. This information is sponsored by Blitz Motorsports and Yamaha and Mystery Ranch. This forecast does not apply to operating ski areas.

Mountain Weather

Since yesterday the mountains received 7-9” of snow near West Yellowstone and in the southern Madison range, 6” near Cooke City, 1” in Hyalite and zero near Big Sky and the Bridger Range. Overnight, temperatures rose to the high teens and low 20s F, and wind was south-southwest at 10-25 mph with gusts of 30-50 mph. Today, temperatures will drop through the teens into single digits F by tonight, and wind will be southwest at 15-25 mph with gusts of 30-45 mph. Snow will continue near West Yellowstone and Cooke City and begin in Big Sky and Bozeman later this morning. Another 4-6” of snow is possible throughout the advisory area today.

Snowpack and Avalanche Discussion

In the mountains near Cooke City 2-3 feet of snow fell since Wednesday equal to 3” of snow water equivalent (SWE). Avalanches breaking in the new snow are likely, especially where it has been drifted into stiffer slabs. For the last couple weeks these mountains received steady snowfall with minimal avalanche activity reported. But don’t let your guard down. A snowpack can’t be trusted until it has time to adjust and show how it holds up to each storm. Today, more snow and moderate southwest winds mean avalanche conditions remain dangerous. A person can trigger an avalanche breaking below recent new snow, and possibly deeper in the snowpack which would be large and potentially deadly. Stay off and out from underneath slopes steeper than 30 degrees. The avalanche danger is rated CONSIDERABLE.

Near West Yellowstone and in the southern Madison and southern Gallatin ranges dangerous avalanche conditions exist where moderate to strong southerly wind has drifted snow into fresh slabs. These wind slabs will be unstable today as they grow larger with additional snow and wind. Since Wednesday these mountains received 2 feet of snow (1.8-2.5” SWE). Avalanches can break multiple feet deep below the recent snow, or possibly break larger on deeper buried weak layers. We have seen signs that buried weak layers are potentially unstable (Lionhead snowpack video, Lionhead avalanches, Tepee avalanches, Bacon Rind collapses), but right now these instabilities do not appear widespread. This indicates some slopes are stable, but we must remain cautious. Today, as the snowpack receives additional weight of new snow and drifts, avoid wind-loaded slopes steeper than 30 degrees and allow time for the snowpack to be tested by this storm (Taylor Fork video). Danger is CONSIDERABLE on wind-loaded slopes and MODERATE on all other slopes.

The Bridger Range, Hyalite and Big Sky received 3-10” of snow (0.3-0.7” SWE) on Friday and can expect a few inches today. Avalanches are possible to trigger where this snow is drifted into stiffer, thicker slabs. Yesterday a natural avalanche broke on a steep, wind-loaded slope on Saddle Peak (photo), and skiers in Beehive saw a recent cornice fall (photo). Watch for signs that drifts of new snow are unstable, such as fresh avalanches or cracks in the snow from your skis. If you see these signs stay off steep, freshly wind-loaded slopes. Right now avalanches breaking deeper in the snowpack are not likely (Saddle Peak video, Buck Ridge video, Beehive video), but we are still keeping an eye out for unstable buried weak layers. Today, the avalanche danger is MODERATE on wind-loaded slopes and LOW on all others.

If you get out, please send us your observations no matter how brief. You can submit them via our website, email (, phone (406-587-6984), or Instagram (#gnfacobs).

Upcoming Education Opportunities:

Get your avalanche brain ready for the season at one of the many classes listed on our education calendar, and list of upcoming events below.

Every Saturday near Cooke City, 10 a.m.-3 p.m. FREE snowpack update and transceiver/rescue training. Stop by for 20 minutes or more at the Round Lake Warming Hut.

Friends of GNFAC Powder Blast Fundraiser

The Friends of the Avalanche Center are hosting the Virtual Powder Blast fundraiser. With only $1,000 left to go, help us reach the $65,000 goal. Your donations support free and low-cost avalanche education, beacon checkers at trailheads, beacon parks, weather stations, and GNFAC programs!

The Last Word

We are sad to report, On Friday in Colorado a skier was killed in an avalanche near Cameron Pass (Link to preliminary report). Our deepest condolences go out to those affected by this tragic accident.

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