Good Morning. This is Alex Marienthal with early season avalanche and weather information from the Gallatin National Forest Avalanche Center on Saturday, November 24th. This bulletin is sponsored by The Friends of the Avalanche Center and Montana State Parks.
Since yesterday morning the mountains got 4-5” of snow near Bozeman, Big Sky and West Yellowstone, and 7” near Cooke City. At 4 a.m. it is snowing and temperatures are high teens to 20s F. Wind is 10-20 mph out of the west to southwest, and will shift to the north-northwest at 20-30 mph this morning. Temperatures will be in the 20s F today and drop to single digits tonight. Snow will continue through the afternoon with 8-12” possible near Bozeman, Big Sky, and Cooke City and 3-5” near West Yellowstone.
The snowpack in the mountains is 3-4 feet deep near Bozeman, Big Sky and Cooke City, and 1-2 feet near West Yellowstone. Generally cold and dry weather since early November created a weak layer on the surface that is now buried below the last couple day’s snowfall. On Wednesday, Doug and I found this weak snow near Cooke City (video, photo) and Eric found it in Hyalite (video). Where the snowpack is deeper, it is mostly strong and supportable below this weak layer.
A few inches of snow and strong wind on Thursday was enough to form unstable conditions between the new snow and old, weak snow surface. The Big Sky ski patrol saw natural and human triggered avalanches during control work, and a skier in Hyalite reported natural avalanches that likely occurred Thursday (photo). More snow and strong wind today will rapidly add weight to now buried weak layers. Natural avalanches are possible as snowfall continues, and avalanches will be easy to trigger where snow is drifted into thick slabs near ridgelines and along edges of gullies.
Be extra cautious today and avoid avalanche terrain. This includes lower angle terrain connected to steep slopes above. The snowpack has been fairly stable and trustworthy this season, but that may change quickly. Resist an urge to ride steep slopes based on previous stable snowpack data. Rapid loading today is a clear sign of decreasing stability. The best defense against avalanches today is conservative, low angle terrain selection.
New this season, we added hyperlinks to the Weather and Avalanche Log and a new Menu item <Avalanches and SnowPits> with information on avalanche activity and incidents.
If you get out and have any avalanche or snowpack observations to share, contact us via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).
Upcoming Avalanche Education and Events
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.
November 26, MSU Snow and Avalanche Workshop, 5-9pm at MSU SUB Ballroom A; http://www.montana.edu/outdoorrecreation/SAW.html
November 29, 30 and Dec 1, 2or 8, Intro to Avalanche w/ Field Day, more info here
December 5, 1-hr Avalanche Awareness, 6-7pm at REI, Bozeman
December 6, 1-hr Avalanche Awareness and Beacon Practice, 6:30-8pm at Story Mill Park
COOKE CITY
Every Friday and Saturday, Rescue Training and Snowpack Update. Friday 6:30-7:30 p.m at the Soda Butte Lodge. Saturday anytime between 10-2 @ Round Lake.
Practice with your rescue gear, and test your partner’s skills. Put fresh batteries in your beacon and check your shovel and probe for any damage, and replace them if needed.