Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Advisory issued on Friday, December 15th at 7:00 a.m. Today’s advisory is sponsored by World Boards and Montana State Parks. This advisory does not apply to operating ski areas.
The mountains did not get any snow since yesterday morning. Wind has been out of the west-northwest in the northern ranges and Cooke City, and out of the west-southwest near West Yellowstone, with speeds of 15-25 mph and gusts to 40 mph. Temperatures this morning are single digits to teens F in the southern ranges, and high 20s F near Bozeman and Big Sky. Today, temperatures will be high 20s to mid-30s F with west-northwest wind at 20-30 mph. A cold front tonight will bring temperatures in the low teens F, and the mountains will get 3-5” of snow by morning with another 3-5” through tomorrow.
Yesterday, strong wind in the Bridger Range drifted 2” of new snow into slabs 6-12” thick. Ski patrol easily triggered these slabs on mid-elevation terrain, at the bottom of cliffs and on steep rollovers. A skier triggered a soft slab on the Football Field just south of Bridger Bowl’s boundary, which ran over the cliffs and left him wide eyed. These soft slabs are possible to trigger today. Carefully evaluate recently wind loaded terrain, and assess the terrain for consequences of being caught in even a small slide.
Eric and I visited the west side of the Bridger Range on Wednesday where we found weak, sugary facets at the surface that will be a problem when capped with more snow (photo, video). I went to the west side again yesterday and was surprised to find a slope with weak facets below the thanksgiving crust, which produced unstable test results (photo, snowpit). Isolated areas of unstable snow exist, especially on the complex terrain of the west side, and give reason to dig before riding steep terrain (video).
Small wind slabs are possible to trigger today and the avalanche danger is MODERATE on wind loaded slopes. Otherwise, the snowpack is generally stable and avalanche danger is LOW on non-wind loaded slopes.
Moderate wind and only a couple inches of fresh snow will not increase the avalanche danger today. The snowpack is mostly stable, and avalanches are difficult to trigger. Small, isolated wind slabs may be found near ridgelines, and will pose minimal threat unless they are triggered in steep, high consequence terrain.
The main concern is weak facets that just got capped by a couple inches of snow (photo). Doug found this layer in the Taylor Fork on Wednesday (photo), and we suspect it exists on slopes throughout the advisory area. Although this layer is not creating widespread instability at the moment, it will be something to pay close attention to as more snow falls this weekend.
Today, generally safe avalanche conditions exist and avalanche danger is LOW.
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
Dec. 21, Avalanche Awareness, 6-7:30 P.m. at Play It Again Sports, 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
Today and tomorrow, Snowmobiler Introduction to Avalanches with Field Course, Info and Register Here
Jan. 6, Avalanche Awareness, 7-8 p.m. at West Yellowstone Holiday Inn Conference Center
COOKE CITY
15 and 16 December, Weekly Current Conditions and Avalanche Rescue, 6:30-7:30 p.m. Friday @ the Super 8, and anytime between 10-2 on Saturday @ Lulu Pass road
A daily checklist is a great way to help prevent common mistakes or overlooking important data when travelling in the backcountry. This article from Backcountry Magazine discusses how to use and create your own backcountry checklist.