Good morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Advisory issued on Thursday, December 17, at 7:30 a.m. Today’s advisory is sponsored by Katabatic Brewery and Bridger Bowl. This advisory does not apply to operating ski areas.
At 5 a.m. mountain temperatures are near or below zero degrees F. Winds are westerly around 15 mph, and 3-4” of snow fell overnight. In the last 24 hours the Bridger Range received 16” of low density snow, and other areas received 6-8”. Today will be cold and mostly clear with temperatures reaching the low teens F. Wind will continue out of the west at 15-20 mph with speed increasing tonight. The southern areas will receive light snow this evening, and more snow is expected throughout the mountains this weekend.
Bridger Range
The Bridger Range has received close to 2 feet of snow this week and over 1” of SWE. Yesterday’s low density snow will create loose snow avalanches that could become large enough to knock you over or trigger a larger avalanche. Strong winds prior to yesterday formed wind slabs on a weak snowpack that we observed on Saddle Peak last Sunday (video). New snow and a weak snowpack will make the avalanche danger today HIGH on slopes steeper than 35 degrees and all wind-loaded terrain. Avalanche danger is CONSIDERABLE on all other slopes.
Madison Range Gallatin Range Lionhead area near West Yellowstone Cooke City
The mountains throughout our advisory area contain a weak snowpack. New snow in the last week has added weight to this weak snow and created unstable conditions. Avalanches, collapsing, and shooting cracks are obvious signs that the snowpack is unstable. Doug and I observed all of these signs on Tuesday in the Taylor Fork drainage (video). Snowmobilers near Cooke City had a close call on Tuesday when they triggered and were caught in an avalanche. Skiers in the Northern Gallatin Range yesterday reported a small avalanche that was triggered remotely (photo). We have received reports of avalanches, unstable test results, and a collapsing and cracking snowpack from the mountains near Cooke City (photo) to the mountains near Big Sky.
Slopes with buried weak, sugary snow are unstable (photo). If you step off your skis or sled and sink to the ground you have found this weak layer. Avalanches, shooting cracks, and “whumph” sounds are signs that the snowpack is unstable and you should avoid slopes steeper than 30 degrees. All of these signs have been observed throughout our advisory area. Today, human triggered avalanches are likely and the avalanche danger is rated CONSIDERABLE on all slopes.
SNOTEL sites in SW Montana are not working which impedes our ability to report snowfall amounts. NRCS is working hard to fix this issue soon.
I 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: Snowmobiler Introduction to Avalanches with Field Course
TODAY!!! December 17 and 18, 2015: https /www.ticketriver.com/event/17356
Five hours of lectures are followed by a full day field course. Topics include: avalanche terrain recognition, the affect weather has on avalanche hazard, the development of the mountain snowpack, decision making skills, and basic search and rescue procedures.
Cooke City: December 23, Avalanche Awareness, Cooke City Visitor’s Center, 6-7:30 p.m.