Good morning. This is Eric Knoff with the Gallatin National Forest Avalanche Advisory issued on, Monday December 28, at 7:30 a.m. Today’s advisory is sponsored by Gallatin County Search and Rescue and Bridger Bowl. This advisory does not apply to operating ski areas.
A mostly stable air mass remains over the area producing light winds and partly to mostly cloudy skies. This morning, temperatures range from the mid-teens to low 20s F and winds are swirling 5-10 mph from all directions. Today, increasing clouds and moisture begin to push into the area as a weak storm system approaches from the west. Temperatures will only a warm a few degrees during the day and winds will pick up slightly blowing 10-15 mph out of W-NW. Light snow develops tonight and the mountains should see 1-2 inches by tomorrow morning.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
As days pass without a recent loading event, avalanches are becoming harder to trigger - but the consequences remain high. On Saturday, snowmobilers triggered two large slides near Daisy Pass outside of Cooke City. One slide completely buried a snowmobile (photo, photo). Both of these slides failed on weak facets near the ground. Impacting this deep weak layer is becoming more difficult, but stability tests and avalanche activity indicate that these facets are still very capable of propagating a fracture (video).
Yesterday, Doug and his partner traveled to Hebgen Lake north of West Yellowstone. They didn't experience any cracking or collapsing, likely due to a thick and dense slab, but they did get unstable results in multiple stability tests (video). They chose to play it safe and ski back down their skin track. Other skiers in the same area experienced one large collapse and also got unstable results in stability tests. Skiers near Silver Gate outside of Cooke City also experienced cracking and collapsing along with unstable results in stability tests. Another skier outside of Cooke City observed multiple natural avalanches in alpine terrain, all failing on weak snow near the ground (photo).
All these observations lead to the conclusion that snowpack is still unstable and should not be trusted. Today, terrain management will be the key to safe backcountry travel. Avoiding slopes steeper than 30 degrees will be the best way to avoid avalanches. Although triggering a slide from low on the slope or from a distance is becoming less likely, it does remain a possibility. Watch out for thinner areas of the snowpack such as scoured ridgelines or sub-ridges, rock outcroppings and tree islands. These areas are likely trigger points where it will be easier to impact the buried weak layer. If the weak layer is impacted in a thinner spot, it will likely propagate into a thicker portion of the snowpack, producing a large and dangerous avalanche.
Today – Cautious terrain selection and conservative decision making are essential. Human triggered avalanches are likely and the avalanche danger is rated CONSIDERABLE.
Doug will issue the next advisory tomorrow morning at 7:30 a.m. If you have any snowpack or avalanche observations to share, drop us a line at mtavalanche@gmail.com or leave a message at 587-6984.
EVENTS and AVALANCHE EDUCATION
A complete calendar of classes can be found HERE.
West Yellowstone: January 2, 1hr Avalanche Awareness, West Yellowstone Holliday Inn, 7-8:30 p.m.
Bozeman: January 6, Women’s Avalanche Awareness and Beacon 101, Beall Park, 6-8 p.m.
January 9 and 10, Companion Rescue Clinic, REI, Fri 6-8p.m., Sat 10a.m.-2p.m.
January 13, 1hr Avalanche Awareness, REI, 6-7:30 p.m.
Livingston: January 14, 1hr Avalanche Awareness, Neptune’s Brewery, 6-7:30 p.m.
Dillon: January 19, 1hr Avalanche Awareness, UM Western Library, 6:30-8 p.m.
ASMSU Intro to Avalanches w/ Field Course
January 20, 21 and 23 or 24: https://www.ticketriver.com/event/16861
The workshops will be held on Wednesday and Thursday evenings, with a field course on either Saturday or Sunday. Different topics will be presented each evening. Topics include: avalanche terrain recognition, the effect weather has on avalanche hazard, the development of the mountain snowpack, decision making skills, and basic search and rescue procedures.