Good Morning. This is Eric Knoff with the Gallatin National Forest Avalanche Advisory issued on Saturday, December 16th at 6:30 a.m. Today’s advisory is sponsored by Knoff Group Real Estate and Yellowstone Ski Tours. This advisory does not apply to operating ski areas.
At 5 a.m. the mountains have picked up 2-3” of new snow. Currently, it’s still snowing lightly and temperatures are in the teens to low 20’s F. Winds are blowing 5-15 mph out of the west. Today, snow will continue through the morning hours and the mountains will pick up an additional 1-3” by this afternoon. Skies begin to clear later in the day and temps will warm into the 20’s F. Winds will continue to blow 5-15 mph out of the west. No snow is expected tonight through tomorrow.
This storm looks to be weaker than originally forecasted. By the time it’s over, the mountains will likely pick up 3-5” of low density snow. This won’t add a significant amount of stress to the snowpack, but it will be enough produce heightened avalanche conditions. On some slopes, the new snow is being deposited on a weak layer of near surface facets that formed during the recent high pressure. Alex and I found this layer on the west side of the Bridger Range (photo, video) and I also found it in the Lionhead area near West Yellowstone yesterday. It’s safe to say this persistent weak layer exists throughout the advisory area (photo).
Today, human triggered avalanches will be possible on wind loaded and non-wind loaded slopes. In areas where the new snow has been deposited over a weak old snow surface, it will be possible to trigger small soft slab avalanches in steeper terrain. These slides won’t carry a tremendous amount of volume, but they could easily catch and carry a skier or rider into unfavorable terrain. Watch for signs of instability such as cracking/collapsing and avoid slopes where these signs are present.
Fortunately, this storm did not arrive with a heavy amount of wind, so wind loading won’t be a major concern. There will be small isolated wind slabs near the ridgelines, but these should be easy to recognize and avoid. In the Bridger Range, wind slabs that formed prior to this storm could still be a problem. On Thursday, a skier triggered a wind slab on the Football Field south of Bridger Bowl that ran over the cliffs hundreds of feet below. Today, these older slabs should be more stubborn, but they’re something to keep in mind when traveling in the backcountry around the Bridgers. In all areas, manage you’re terrain carefully.
Today, human triggered avalanches are possible and the avalanche danger is rated MODERATE.
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
Events and Education Calendar
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
Today, Avalanche Rescue, 10-2 on @ 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.