Good morning. This is Dave Zinn with the Gallatin National Forest Avalanche Forecast on Thursday, December 8th at 7:00 a.m. This information is sponsored by Blitz Motorsports and Yamaha and the Yellowstone Club Community Foundation. This forecast does not apply to operating ski areas.
Please consider donating to the Friends of GNFAC Annual Fundraiser.
*Note: Bridger Bowl Ski Area IS CLOSED TO ALL uphill travel as they prepare for Friday’s opening. It will remain closed to uphill travel for the duration of their season.
This morning, temperatures are in the single digits to mid-teens F with 5 to 15 mph winds from the west to southwest and there is no new snow. Today, temperatures will rise to the upper teens to mid-20s F with 5 to 15 mph winds from the south to the southwest. A small storm favoring the mountains near West Yellowstone will pass through tomorrow, with more snow arriving later this weekend.
In the mountains south of Big Sky and around West Yellowstone and Cooke City, strong winds the first half of the week drifted recent snow into thick slabs sitting on top of weak, faceted snow. On Tuesday, a snowmobiler triggered a large avalanche that broke on weak snow near the ground at Chimney Rock near Cooke City. We have limited details but thankfully, everybody made it out (limited details). Recent natural avalanches in the Taylor Fork in the Southern Madison Range and near Henderson Bench outside Cooke City demonstrated the snowpack was teetering on the edge of failure (TF details, Henderson photo and details).
Today, natural avalanches are unlikely; however, human-triggered avalanches breaking 2-3 feet deep remain a deadly possibility. Yesterday, Ian rode into the Taylor Fork and found a thick layer of weak facets buried 18-24” deep (video). It isn’t everywhere, but it exists on many slopes in the Southern Madison and Southern Gallatin Ranges and near West Yellowstone and Cooke City.
Dig down to assess for the presence of this persistent weak layer. If you find it, stay in terrain less than 30 degrees steep. The avalanche danger is MODERATE because human-triggered avalanches are possible.
In the mountains around Bozeman and Big Sky, the primary concern is avalanches failing on steep slopes with recent drifts of wind-loaded snow. Indicators of these areas of concern include cracking, a stiff snow surface or a hollow “drum” like feel, cornices, and visible drifts.
Yesterday, the Big Sky Ski Patrol triggered 12-18” deep wind-slab avalanches in their alpine terrain. The Bridger Bowl Ski Patrol performed their first round of avalanche mitigation, noting that most slides involved the recent layers of wind-loaded snow. Three days ago, two skiers ascending a steep couloir triggered an avalanche on a wind-loaded slope. At times they were completely submerged in the avalanche, but thankfully they didn’t hit any trees or rocks and came to rest on the surface (details and photos). Watch my video from Divide Peak earlier this week to hear our concerns about snow transported by the wind.
Today, find higher quality and safer skiing and riding on non-wind-loaded terrain. Dig and test for any deeper instabilities before committing to a slope. Human-triggered avalanches are possible, and the danger is rated MODERATE.
If you get out, please share avalanche, snowpack or weather observations via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).
In the mountains around Island Park, strong winds the first half of the week drifted recent snow into thick slabs. In the nearby Lionhead area, these slabs are sitting on top of weak, faceted snow and we are concerned that the same conditions exist in the Centennial Range. While natural avalanches are unlikely today, dangerous human-triggered avalanches breaking 2-3 feet deep remain a deadly possibility. If you intend to ride or ski in avalanche terrain, avoid wind-loaded terrain, and dig down to assess for the presence of this persistent weak layer. If you find it, stay off steep slopes, and send us an observation to let us know what you discovered.
Ian and I will be in Island Park hunting for weak layers tomorrow. Tomorrow evening, visit the Island Park Trip Planning page to learn what we find and watch our field video.
Upcoming Avalanche Education and Events
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.
TONIGHT, Thursday, December 8, 6 - 7:30 p.m., Free Snow & Avalanche Safety Workshop: Belgrade Community. This workshop will cover the basics of snow and avalanche equipment. Belgrade Community Library. A raffle and pizza will be included!
Monday, December 12, 5-8 p.m. @MAP Brewing, Movie Night.
Tuesday, December 13, 6 p.m., Avalanche Awareness + Beacons at Story Mill Park. Free.
Watch our playlist of YouTube videos to get caught up on our avalanche concerns this season.