Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Advisory issued on Sunday, December 24th at 7:00 a.m. Today’s advisory is sponsored by the Community Food Co-op and Bridger Bowl. This advisory does not apply to operating ski areas.
Temperatures are below zero F this morning and will reach the low teens F today. The mountains did not get any snow overnight, and wind has been out of the west-northwest at 20-30 mph since yesterday morning. The cold northwest flow will continue today with clear skies and ridgetop wind speeds at 15-25 mph. The mountains will get a couple inches of new snow early Christmas morning with 3-5” possible through the day.
The Lionhead area near West Yellowstone has 4 feet of snow on the ground with 1.5 feet of new snow since Wednesday. This new snow rests over weak, sugary facets above a firm crust and creates dangerous avalanche conditions (video). Snowmobilers or skiers can easily collapse this unstable snowpack and trigger large avalanches. Be extra cautious if travelling on or below slopes steeper than 30 degrees. Avalanches are possible to trigger from flat terrain and low on slopes. Expose only one person at a time when riding or crossing below steep slopes.
Today, avalanches are easy to trigger on and below steep slopes and the avalanche danger is CONSIDERABLE.
Near Bozeman and Big Sky the mountains have 4-5 feet of snow on the ground, and near Cooke City there is 6-8 feet. New snow since Wednesday totaled 14-20” and was very low density. Yesterday, moderate to strong northwest wind drifted new snow into slabs near ridgelines (photo), and these slabs will continue to grow today. These wind slabs are 1-3 feet deep, easy to trigger, and could be wide and extend far downslope. Be cautious of wind loaded slopes and large cornices. Avoid steep slopes if you see cracking and collapsing of the snow, and minimize exposure to high consequence terrain like steep slopes above cliffs.
Secondary to wind slabs, there are some slopes where it is possible to trigger an avalanche on a layer of facets 2-3 feet deep. I rode around the mountains near Cooke City the last two days and searched for unstable snow without success (video). Eric looked for this layer at Taylor Fork on Thursday, and also found stable snow in his snow pits (video). A few small avalanches have been observed on this layer of facets (photo, photo) and it is weaker in some areas (W. side of Bridgers). It is worth digging 3 feet to test for this instability before riding steep terrain.
Today, wind slabs are easy to trigger and the avalanche danger is CONSIDERABLE on wind loaded slopes and MODERATE on non-wind loaded slopes.
If you get out and have any avalanche or snowpack observations to share, drop a line via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).
Upcoming Avalanche Education and Events
BOZEMAN
Jan. 12 and 13, Companion Rescue Clinic, Info and Register
Jan. 17, 18 and 20 or 21, Introduction to Avalanches w/ Field Day, Info and Register Here
Jan. 24, 25 and 27, Advanced Avalanche Workshop w. Field Day, Info and Register Here
Feb. 9 and 10, Companion Rescue Clinic, Info and Register
WEST YELLOWSTONE
Jan. 6, Avalanche Awareness, 7-8 p.m. at West Yellowstone Holiday Inn Conference Center
COOKE CITY
Every Friday and Saturday, Current Conditions and Avalanche Rescue, Friday 6:30-7:30 p.m. at Super 8 next week, and Antler's Lodge in January. Saturday anytime between 10-2 @ Lulu Pass road.
Check out Chabot’s article, Being Prepared that was just published in the Chronicle’s CARVE magazine this weekend. In essence, preparation decreases the chance for negative outcomes.