GNFAC Avalanche Forecast for Sat Feb 20, 2021

Not the Current Forecast

Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Forecast on Saturday, February 20th at 7:05 a.m. Today's forecast is sponsored by Summit Motorsports and Ski-Doo and Upper Yellowstone Snowmobile Club. This forecast does not apply to operating ski areas.

Mountain Weather

Since yesterday morning the mountains near West Yellowstone and Cooke City got 3-4” of snow, and elsewhere got 1-2”. Yesterday wind was west-southwest at 10-20 mph with gusts of 30-40 mph. This morning wind is 5-10 mph with gusts of 15-20 mph, and temperatures are teens to low 20s F. Today temperatures will be high teens to mid-20s F. Wind will shift to the northwest at 5-15 mph with gusts to 25 mph, then will increase tonight. Light, scattered snow showers today will drop 1-2” in the southern half of our advisory area with less than inch near Bozeman.

Snowpack and Avalanche Discussion

In the Bridger Range, Hyalite and near Big Sky strong wind the last two days drifted the recent 2-3 feet of snow into thick slabs. Yesterday, skiers near Mt. Blackmore reported a 3-4 foot deep, 500 foot wide natural avalanche which they had not seen on Thursday morning (photos and details), and ice climbers saw a relatively large recent avalanche near Maid of the Mist (photo and details). On Thursday near Bridger Peak, a large avalanche broke on a heavily wind loaded slope (photos). Yesterday Ian and I snowmobiled on Buck Ridge near Big Sky. We did not see recent avalanches, but weak, sugary snow near the ground is underneath 4-6 feet of snow and can’t be trusted (video). While it is becoming more difficult to collapse this deep weak layer, recent activity shows that if you do trigger an avalanche it could be destructive and deadly.

Today, avoid travel on and underneath steep, wind-loaded slopes where triggering a large avalanche is likely. Avalanche danger is CONSIDERABLE on wind-loaded slopes and MODERATE on all other steep slopes.

In the southern Gallatin and Madison Range and near West Yellowstone, weak, sugary snow near the ground makes large avalanches possible. Earlier in the week these mountains did not receive the same heavy snow as the northern part of our area. This makes it less likely to trigger a large avalanche, but the potential size is the same as we have seen recently near Bozeman and Big Sky. A large snowmobile triggered slide in Cabin Creek last week is another example of what is possible (details). Three to five inches of snow that fell since yesterday and light wind today will unlikely push the snowpack to break naturally, but could push some slopes closer to sliding under the weight of a person. Today, large avalanches are possible to trigger and avalanche danger is MODERATE.

In the mountains near Cooke City a snowmobile triggered avalanche on Crown Butte on Thursday is evidence that avalanches can be triggered (photo, photo). Recent snow and wind formed fresh drifts that can break under the weight of a skier or rider. Four to five inches of new snow today adds weight to these drifts. Be extra cautious of wind-loaded slopes, near ridgelines and below cornices. We can’t rule out the possibility of triggering a deeper slide on slopes with shallower snow (see Dave’s videos from Wednesday, Thursday). Today the avalanche danger is rated MODERATE. Carefully evaluate the snowpack and consequences of a slide before travel on or underneath steep slopes.

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


We posted a detailed report from Sunday's fatal avalanche in Beehive Basin here.

The video of our accident investigation from the field is here.

Upcoming Avalanche Education and Events

See our education calendar for an up-to-date list of all local classes. Here are a few select upcoming events and opportunities to check out:

Every Saturday in Cooke City, FREE snowpack update and rescue practice at the Round Lake Warming Hut between 10 a.m. and 3 p.m. Poster with More Info.

February 22, 6-7 p.m., Forecaster Chat: Rethinking Avalanche Terrain from a Strategic Perspective, Hosted online by Uphill Pursuits, Link to Join HERE

The Last Word

Yesterday a snowmobiler was killed in an avalanche in Idaho (preliminary report from S.A.C.). This was the 23rd person killed by an avalanche in the U.S. since January 30, and the 29th avalanche fatality this winter.

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