GNFAC Avalanche Forecast for Mon Jan 18, 2021

Not the Current Forecast

Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Forecast on Monday, January 18th at 7:30 a.m. This forecast is sponsored by Gallatin County Search and Rescue and Werner Wealth Management (Advisors with DA Davidson). This forecast does not apply to operating ski areas.

Mountain Weather

At 6am the mountains have 6” of new snow in Hyalite, 4” near Cooke City, and 1-2” elsewhere. Temperatures are single digits to teens F, and wind is northwest at 10-20 mph with gusts to 30 mph. Yesterday afternoon winds gusted 40-60 mph. Today, snow is expected with temperatures in the teens to low 20s F and northwest wind at 15-30 mph. Through today, 3-6” more snow is possible near Bozeman, Big Sky and Cooke City with 1-2” near West Yellowstone.

Snowpack and Avalanche Discussion

Current snowfall is favoring the northern Gallatin Range with 6” of new snow this morning (0.6” snow water equivalent) with more forecast to fall today. This snow is falling on a weak snowpack and creates dangerous avalanche conditions. Human triggered avalanches are likely and natural avalanches are possible. Avoid travel on and underneath steep slopes. The avalanche danger is CONSIDERABLE.

The Bridger Range and mountains near Big Sky got an inch of snow yesterday. More snow today with moderate northwest wind will form fresh slabs on a weak snowpack. Weak, sugary snow near the ground, buried 2-3’ deep has produced large human triggered and natural avalanches over the last couple weeks (avalanche log). Additionally, a layer of weak, feathery surface hoar is buried 3-6” below recent snow. Where today’s new snow is drifted into thicker slabs it will avalanche easily on the surface hoar layer, and avalanches can break deeper on sugary snow near the ground (video). Avalanche danger is CONSIDERABLE on wind-loaded slopes and MODERATE on all other slopes.

Near Cooke City, 4” of new snow this morning (0.4” SWE) with more snow and wind today will grow thicker slabs over recently buried surface hoar. Dave rode north of Cooke yesterday and found this surface hoar layer which he discuses is his video. Over the weekend skiers got collapsing with long shooting cracks (photo, photo), and triggered a small slab on this layer (photo). An additional concern is weak, sugary snow buried 2-3 feet deep which makes larger avalanches possible. These weak layers are not on every slope, so it is worth digging to check for them and track their distribution and stability. With snow and wind adding weight to the snowpack today, avoid steep wind-loaded slopes. Carefully assess the snowpack before riding any steep slope. Avalanche danger is CONSIDERABLE on wind-loaded slopes and MODERATE on all other slopes.

The mountains south of Big Sky to West Yellowstone have one inch of new snow and will receive a couple inches of snow today. With minimal loading, the chances have decreased for triggering an avalanche on weak snow near the ground, but this snow is slow to gain strength. Even a little snow today will add weight to an unstable snowpack. Travel in avalanche terrain requires thorough snowpack assessment and cautious terrain selection. The best strategy is to avoid travel on and underneath slopes steeper than 30 degrees. Large avalanches are possible to trigger and danger is MODERATE.

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 Avalanche Education and Events

See our education calendar for an up-to-date list of all local classes. Here are a few select upcoming events and opportunities to check out:

Every Saturday in Cooke City, FREE snowpack update and rescue practice at the Round Lake Warming Hut between 10 a.m. and 3 p.m. Poster with More Info.

Tuesday, January 19, 6-7 p.m. The Friends of the Avalanche Center will offer a FREE 1-hr Avalanche Awareness Talk in partnership with the University of Montana Western School of Outreach. The talk will be a live, ONLINE event. Join us HERE

January 20 & 21 (plus field sessions the following weekends), Avalanche Fundamentals with Field Course. There are separate field sessions tailored for both skiers and splitboarders (Bridger Bowl) and snowmobilers (Buck Ridge). Register here.

The Last Word

Ski-Doo is offering free avalanche education classes online that you can take here: