GNFAC Avalanche Forecast for Sun Dec 19, 2021

Not the Current Forecast

Good morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Forecast on Sunday, December 19th at 7:00 a.m. This information is sponsored by The First National Bank of Gilbert, MN and Gaia GPS. This forecast does not apply to operating ski areas.

Bridger Bowl will be closed to uphill travel starting at dark tonight (12/19). Please stay off the hill tonight and tomorrow as they prepare to open Tuesday (12/21). Thank you.

Mountain Weather

Yesterday the mountains near Cooke City got 1-2” of snow with zero to a trace elsewhere. Overnight, west-southwest wind increased to 15-35 mph with gusts of 40-73 mph. This morning temperatures range from single digits near Cooke City and West Yellowstone to low 30s F near Bozeman. Today temperatures will be high 20s to low 30s F with west-southwest wind at 30-55 mph. Snow is expected tonight with 5-8” possible near Cooke City, Big Sky and Bozeman, and 1-3” near West Yellowstone.

Snowpack and Avalanche Discussion

Strong west-southwest wind will drift snow from the past week into fresh slabs that skiers or riders could trigger. A person could also trigger avalanches of older drifts that formed over the past week. These wind slabs could range from 6 inches to 4 feet in depth. Avalanches are possible similar to those recently triggered by skiers and riders, such as a skier triggered slide at Bridger on Thursday (photos and details), a snowmobile triggered slide in the Taylor Fork (video), and a skier triggered avalanche at Bacon Rind on Wednesday (photo). Be extra cautious of wind-loaded slopes, especially in terrain where the consequences being caught in a slide are high, like where you would be pushed into trees, over cliffs, dragged through rocks, or buried deeply in a confined gully.

Additionally, if you plan to ski or ride steep slopes dig to look for and evaluate the stability of buried weak layers. We have seen minimal evidence to indicate widespread buried weak layers exist, but with each load of new snow or fresh wind slabs we could see avalanches break deeper in the snowpack. Stay on the lookout for unstable buried weak layers, especially on slopes that held snow from October and early November.

Today, avalanches are possible to trigger and the avalanche danger is MODERATE.

Near Cooke City, strong west-southwest wind will drift snow into fresh wind slabs that skiers or riders could trigger. Older wind slabs 1-3 feet thick that formed over the past week are also possible to trigger, similar to a slab that snowmobilers triggered on Wednesday near Goose lake (details). On non-wind loaded slopes avalanches are unlikely. If you plan to ski or ride steep slopes dig to look for potential unstable buried weak layers, and carefully assess the stability of wind-drifted snow.

The avalanche danger is MODERATE on wind-loaded slopes and LOW on all other slopes.

If you get out, please send us your observations no matter how brief. You can submit them via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).

Upcoming Education Opportunities:

Get your avalanche brain ready for the season at one of the many classes listed on our education calendar, and list of upcoming events below. Don’t delay preparing and inspecting your avalanche gear. Get some tips from Dave Zinn in this Pre-Season gear check video.

Every Saturday near Cooke City, 10a.m.-3p.m. FREE snowpack update and transceiver/rescue training. Stop by for 20 minutes or more at the Round Lake Warming Hut.

Friends of GNFAC Powder Blast Fundraiser

The Friends of the Avalanche Center are hosting the Virtual Powder Blast fundraiser. With only $2,000 left to go, help us reach the $65,000 goal. Your donations support free and low-cost avalanche education, beacon checkers at trailheads, beacon parks, weather stations, and GNFAC programs!

The Last Word

Sadly, On Friday two teenagers died in an avalanche outside of Driggs, Idaho in the Big Hole Mountains. Details so far are sparse, but initial reports are that they were skiing and snowmobiling (Link to news story).


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