Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Wednesday, January 6, at 7:30 a.m. Today’s advisory is sponsored by Javaman and Bountiful Table. This advisory does not apply to operating ski areas.
Snow flurries continued around Big Sky to West Yellowstone and Cooke City yesterday measuring 1-2 inches with light southwest winds and temperatures slightly above freezing. At 5 a.m. the skies are clear, mountain temperatures are in the low 20s and ridgetop winds are blowing south to southwest at 10-15 mph with an occasional gust of 25 mph. Today will be mostly sunny with increasing clouds in the southern mountains later this afternoon. Early tomorrow morning snow flurries will start and continue through the day.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
Yesterday, 1- 2 inches of 6-7% density powder fell around Big Sky and to the south. This was in addition to the 1-2 inches that fell the day before. Ridgetop winds have been light, but still strong enough to blow this powder into wind slabs burying a layer of near-surface facets (small grains of sugary snow) creating an unstable interface. The Big Sky Ski Patrol avalanched these thin wind slabs with their skis and I expect folks in the backcountry could too. Eric and I found these facets in Lionhead on Sunday (video) and have gotten reports that this layer is widespread.
Unlike today’s wind slabs, which can be found near the ridgelines and avoided, a weak layer of depth hoar crystals at the ground are not so easily dismissed. These big, sugary grains underlie our snowpack and avalanched both naturally and with human triggers over Christmas and New Year’s, documented on our Photos page. The good news is that this layer is slowly gaining strength and becoming harder to trigger. The bad news is that this depth hoar will linger for weeks, maybe months, potentially avalanching from the weight of an unlucky skier or rider. The likelihood of triggering avalanches has decreased, but not gone. Trigger points are typically found on thinner areas of the snowpack, sometimes near buried rock outcroppings or on the edges of a slope, but they are not obvious. Alex describes how triggering avalanches on depth hoar is low probability with high consequences in this video.
The danger level is rated MODERATE on all slopes throughout our advisory area since wind slabs can be easily triggered and deeper avalanches running at the ground are still possible.
Alex 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.
EVENT in Bozeman: January 19, 5:30-7 p.m. and 7:30-9 p.m., Avi Center Beer Social at Montana Ale Works. Fundraiser for the Friends of the Avalanche Center, $35. Tickets here: https://www.ticketriver.com/event/18542
TONIGHT in Bozeman: January 6, Women’s Avalanche Awareness and Beacon 101, Beall Park, 6-8 p.m.
January 8 and 9, Companion Rescue Clinic, REI, Fri 6-8p.m., Sat 10a.m.-2p.m.
January 13, 1hr Avalanche Awareness, REI, 6-7:30 p.m.
Four Corners: January 13, 1hr Avalanche Awareness for Snowmobilers, GVSA Groomer Building, 7-8 p.m.
West Yellowstone: January 9, 23, and 30, 1hr Avalanche Awareness, West Yellowstone Holliday Inn, 7-8:30 p.m.
Livingston: January 14, 1hr Avalanche Awareness, Neptune’s Brewery, 6-7:30 p.m.
Cooke City: January 16, 1hr Avalanche Awareness, Visitor’s Center, 6-7:30 p.m.
January 30, Companion Rescue for Snowmobilers, https://www.ticketriver.com/event/18078
Dillon: January 19, 1hr Avalanche Awareness, UM Western Library, 6:30-8 p.m.
January 23 and 24, Intro to Avalanches w/ Field Course, https://www.ticketriver.com/event/18441
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.
Advanced Avalanche Workshop w/ Field Course
January 27, 28, and 30: https://www.ticketriver.com/event/16862
Course content includes: snowpack metamorphism, the mechanics of avalanche failure and fracture, and decision-making. Different topics are covered each evening session. The field session includes snowpack analysis and avalanche rescue scenarios.