Good morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Forecast on Sunday, February 19th at 7:20 a.m. This information is sponsored by World Boards and Archer Construction. This forecast does not apply to operating ski areas.
Yesterday and last night the Bridger Range received 20” of snow, Hyalite and Big Sky got 5-10”, and 1-2” fell near Cooke City and West Yellowstone. Wind shifted from the southwest to west-northwest at 5-20 mph with gusts of 25-40 mph. This morning temperatures are single digits to teens F, and today will reach teens to mid-20s F. Wind will be out of the west-northwest, and will increase to 15-30 mph with gusts to 45 mph. Light snow through today will deliver 1-3” by this evening. Tonight an additional 3-5” are likely with up to a foot possible near Cooke City by morning, and heavy snow will continue through tomorrow and Tuesday.
In the Bridger Range, 20” of new snow (1.2” snow water equivalent (SWE)) and increasing west wind creates very dangerous avalanche conditions on wind-loaded slopes. Human-triggered and natural avalanches are likely, especially where the new snow is drifted into thicker slabs. Avalanches of new and wind-drifted snow will be large enough to bury a person, and there is a chance larger avalanches will break deeper on older buried weak layers. Avoid travel on and underneath steep, wind-loaded slopes. Conservative decision making and cautious route finding are essential today. With wind expected to increase and a few more inches of snow, stability will get worse. Avalanche danger is HIGH on wind-loaded slopes and CONSIDERABLE otherwise.
In the northern Gallatin Range, moderate to strong wind will drift 8” of new snow (0.6” SWE) into denser, thick wind slabs that are easy for a person to trigger. On wind-loaded slopes, human triggered avalanches are likely and could be large enough to bury or injure a person. On non-wind loaded slopes avalanches could break below the new snow, possibly on weak layers buried 2-3 feet deep. Be extra cautious of wind-loaded slopes, and carefully assess the stability of new snow and buried weak layers before riding or crossing any steep slope. Avalanche danger is CONSIDERABLE on wind-loaded slopes and MODERATE on non-wind loaded slopes.
In the Madison Range and southern Gallatin Range 5-10” of low-density snow (0.2-0.4” SWE) creates heightened avalanche conditions. A person can trigger a slab of freshly drifted snow which may be large enough to bury you, but even a small drift can be dangerous if it carries you into a terrain trap like trees or over a cliff. The weight of fresh drifts may cause avalanches to break deeper and wider on weak layers buried 1-3 feet deep. Before riding steep slopes, carefully evaluate the snowpack for fresh drifts and buried weak layers. Avalanche danger is MODERATE.
Near Cooke City and West Yellowstone, a person can trigger avalanches that break in recently formed drifts of snow, or fresh drifts that form as snow falls later today (photo). Recent wind out of the north and west drifted snow into thicker slabs, and two days ago, riders north of Cooke City saw a recent snowmobile triggered slide on Crown Butte (details). Today, new snow will be drifted into fresh slabs that can be triggered by a skier or rider. Before riding steep slopes, carefully evaluate the stability of recently formed drifts. Avalanches on weak layers buried 1-3 feet are currently unlikely, but it is worthwhile to dig to assess these weak layers before riding steep slopes (Lionhead video). Avalanche danger is MODERATE on wind-loaded slopes and LOW on non-wind loaded slopes.
Expect avalanche danger to rise overnight and tomorrow. If heavy snowfall begins early today, fresh unstable drifts may form and cause danger to increase by this evening.
Please share avalanche, snowpack or weather observations via our website, email (email@example.com), 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.
February 19, 10 a.m.-2p.m. Companion Rescue Clinic Field Day in the Bozeman area. Required Online Classroom Session at 6 p.m. on Feb 18. Information and course registration are HERE.
March 3-5, Bozeman Splitfest. More info and register here.
Every Saturday, 10 a.m. - 2:00 p.m. Avalanche Rescue Training, drop in for any amount of time. Round Lake Warming Hut, Cooke City. Free.
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.