This is Dave Zinn with the avalanche forecast for Saturday, December 28th, at 7:00 a.m. This forecast is sponsored by Alpine Orthopedics & Sports Medicine, Stronghold Fabrication and Knoff Group Real Estate. This forecast does not apply to operating ski areas.
This morning, mountain temperatures are in the teens and 20s F with 15-25 mph winds from the west and southwest. In the last 24 hours, most of the forecast area has received 2-4” of new snow (0.2-0.3” Snow Water Equivalent - SWE), with a trace to 1” near Bozeman.
Storm Totals Since Wednesday:
- Big Sky – 12-15” (1” SWE)
- Island Park, West Yellowstone, and Cooke City – 8-13” (0.7-1.1” SWE)
- Bridger and Northern Gallatin Range – 5-8” (0.5-0.7 SWE)
Today, high temperatures will reach the 20s and low 30s F with 15-25 mph winds from the west and southwest. The mountains near Island Park, West Yellowstone and Cooke City will receive 4-7” of snow by Sunday morning, with 1-2” near Bozeman and Big Sky.
While dangerous avalanche conditions persist in the mountains around Island Park, West Yellowstone, Big Sky and Cooke City, we are allowing the Avalanche Watch to expire as less snow has fallen than anticipated. Intensifying snow on Sunday may still lead to an Avalanche Warning before the storm is over.
New and wind-drifted snow is overloading widespread, persistent weak layers buried 1-2 feet deep (West Yellowstone, Island Park, Bacon Rind, Bridgers videos). Human-triggered persistent slab avalanches are likely on slopes steeper than 30 degrees. Backcountry travelers could trigger slides that break remotely on nearby slopes above, below or to the side, necessitating cautious route-finding. While wind-loaded areas are the most unstable, all steep slopes are suspect.
Yesterday, riders near West Yellowstone reported collapses and shooting cracks, and skiers south of Cooke City avoided steep slopes after getting very unstable test results. The day before, cracks shooting up to 100 feet in the southern Madison Range were eye-opening (observation page). When red flags indicating instability, including avalanches, collapsing and shooting cracks, are present, snowpits and tests are not required, but a cautious travel plan that largely avoids avalanche terrain and runout zones is.
Enjoy the new snow on slopes under 30 degrees without steep terrain immediately uphill. The avalanche danger is CONSIDERABLE.
Weak layers buried 1-2 feet deep in the Bridger and Northern Gallatin Ranges make triggering a persistent slab avalanche possible. However, with less recent snow than other portions of the forecast area, the likelihood is lower. Yesterday, a small, natural wind slab on Saddle Peak was a reminder of a secondary avalanche concern (details). Mark and I found a stronger-than-average snowpack in the Divide Peak Basin yesterday, but variability across a mountain range and known weak layers resist blanket statements, especially this early in the season (media and observation).
Avoid wind-loaded slopes where persistent slab and wind slab avalanches are most likely. Evaluate the snowpack for instability before considering steep terrain in wind-sheltered areas. Move to lower-angle terrain in the presence of recent avalanche activity, cracking, collapsing and unstable test scores.
The avalanche danger is MODERATE.
Enjoy the new snow, send in your snowpack observations and have a safe weekend.
Upcoming Avalanche Education and Events
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar
Monday, December 30, 6-8 p.m., Free Avalanche Awareness and Conditions Update, MAP Brewing.
We offer Avalanche Fundamentals with Field Session courses targeted towards non-motorized travelers in January and one geared towards motorized users. Sign up early before they fill up.
Every weekend in Cooke City: Friday at The Antlers at 7 p.m., Free Avalanche Awareness and Current Conditions talk, and Saturday from 10 a.m.-2 p.m. at Round Lake Warming Hut, Free Rescue Practice.
Friends of the Avalanche Center: Fall Fundraiser!
We’re still counting on your support and the online Fall Powder Blast fundraiser is 80% of the way to our goal. Please consider making even a small donation HERE or via Venmo