GNFAC Avalanche Forecast for Tue Dec 10, 2019

Not the Current Forecast

Good Morning. This is Doug Chabot with the Gallatin National Forest Avalanche Forecast on Tuesday, December 10th at 7:00 a.m. Today’s forecast is sponsored by Stronghold Fabrication and Alpine Orthopedics. This forecast does not apply to operating ski areas.

Mountain Weather

At 5 a.m. there is no new snow to report. Mountain temperatures are in the teens and west winds are averaging 10-20 mph with gusts of 30 mph. Today will be mostly sunny. Temperatures will be in the high 20s and winds will blow at 5-15 mph from the west.

Snowpack and Avalanche Discussion

The mountains from Big Sky to West Yellowstone have weak, sugary snow near the ground that is breaking. On Sunday, skiers in Lionhead near West Yellowstone had collapses and cracks shoot out from their feet (photo) while snowmobilers on Buck Ridge saw natural avalanches (photo, photo). Yesterday the Big Sky Ski Patrol triggered a large, 2 foot deep avalanche with explosives that broke on these facets. Sunday’s 8-10” of snow and wind-loading will continue to burden this unstable snowpack (photo, video). Today, triggering avalanches on skis or a sled is likely. The snowpack is shallow, its structure is poor and is not expected to strengthen quickly. Watch your slope angles and stay clear of avalanche terrain as the danger is rated CONSIDERABLE on all slopes.

Outside Cooke City there is a thin layer of weak snow 1.5 feet under the surface. Sunday’s 14” (1.4” of snow water equivalent) added enough stress to make slopes unstable. Snowmobilers triggered a slide on this layer near Lulu Pass and had to be rescued, while another sledder had a near-miss ascending Daisy Pass when a natural slide almost caught him (details, photo). This heavy load also triggered natural slides on Scotch Bonnet (photo) and Miller Ridge. Ian and I went there yesterday and found deep snow, evidence of wind drifts from the strong winds, and a thin layer of facets breaking in our stability tests (video, photo). Today, the avalanche danger is rated MODERATE because it is possible to trigger slides on this layer, although I do not expect it to remain a problem for the long term.  

Alex went to Saddle Peak in the Bridger Range yesterday and was not pleased with his findings. Under a hard slab of wind blown snow he found a weak layer (facets) breaking in his stability tests (video). He and his partner skinned back to the ridge instead of skiing the slope. This was his 4th visit to the range in 8 days and he remains concerned about this layer. Skiers on the Throne near Brackett Creek had cracking a foot deep on wind-loaded slopes, and another party found poor stability on this layer and stayed out of steep terrain (photo). Get used to digging and testing this layer because it is going to be around for a while. It is still possible to trigger avalanches today and the danger is rated MODERATE.

The northern Gallatin Range is the most stable in our forecast area. The 4-6” of snow that fell on Sunday has bonded well to the old surface. Weak snow can be found, especially where the snowpack is thin, but without new snow or fresh wind drifts I do not expect avalanche activity. For today the avalanche danger is rated LOW.

Upcoming Avalanche Education and Events

Our education calendar is full of awareness lectures and field courses. Check it out and plan to attend one or two: Events and Education Calendar.


December 11, 1-hr Avalanche Awareness, 6-7 p.m. at REI.

December 12, Avalanche Awareness + Beacon Practice, 6-8 p.m. at Story Mill Community Center.

December 18, 1-hr Avalanche Awareness, 6-7 p.m. at Uphill Pursuits.


Every Friday and Saturday, Snowpack Update and Rescue Training. Friday, 6:30-7:30 p.m. at the Soda Butte Lodge. Saturday anytime between 10-2 @ Round Lake.


December 17, 1-hr Avalanche Awareness, 6-7 p.m. Elevated Powersports.


December 19, 1-hr Avalanche Awareness, 7-8 p.m. at Choteau High School.

The Last Word

 Sadly, in Colorado a skier was buried and killed in an avalanche on Sunday (Dec 8). This is the first avalanche fatality this season in the U.S. CAIC preliminary report.

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