GNFAC Avalanche Forecast for Sun Feb 21, 2021

Not the Current Forecast

Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Forecast on Sunday, February 21st at 7:15 a.m. Today's forecast is sponsored by Highline Partners and Gallatin Valley Snowmobile Association. This forecast does not apply to operating ski areas.

Mountain Weather

Yesterday the mountains received 2-3” of low-density snow with light west-northwest wind. Overnight, wind shifted west-southwest and increased to 20-30 mph with gusts of 40-55 mph. This morning temperatures are single digits to teens F. Today temperatures will reach mid-20s F and wind will be westerly at 20-35 mph. Light snow showers will drop 1-3” near Cooke City by tomorrow morning with a trace to an inch elsewhere.

Snowpack and Avalanche Discussion

Many natural avalanches broke on weak, sugary snow near the bottom of the snowpack after strong winds a few days ago drifted 2 feet of recent snow into heavy slabs. Today, strong west winds will drift snow into thicker slabs and grow cornices large along ridgelines. The additional weight of a skier, rider or cornice fall could trigger a very large, deep slab avalanche. It is more difficult to collapse this deep weak layer than it was a few week ago, but if you do trigger an avalanche it will be destructive and deadly.

  • Yesterday we skied to Mt. Blackmore and looked at a very large, 4-10 foot deep, 700 foot wide avalanche that broke late Thursday or early Friday (video, photos and details).
  • We also saw a recent natural deep slab avalanche on Alex Lowe peak (photo), and skiers saw a recent very large, deep slide on Flanders peak (photos and details).
  • Near Buck Ridge yesterday, a snowmobiler triggered a deep avalanche, and was luckily not caught (photo).
  • On Thursday near Bridger Peak a large natural avalanche broke on a heavily wind-loaded slope (photos).
  • Last Sunday a splitboarder was killed in an avalanche in Beehive Basin (video). Since then there have been six avalanche fatalities in the U.S., a total of 23 this month and 30 this winter.

Today the avalanche danger is CONSIDERABLE on wind-loaded slopes and MODERATE on all other steep slopes. Avoid travel on and underneath steep, wind-loaded slopes.

In the southern Gallatin and Madison Range and near West Yellowstone, weak, sugary snow near the ground makes large avalanches possible. The potential size of avalanches is similar to those we have seen recently near Bozeman and Big Sky, but less snow and wind through the week lowers the likelihood of triggering an avalanche. These mountains received 1-1.5 feet of snow since last weekend which will be drifted into fresh slabs by wind today. These slabs are possible to trigger and they could break deeper and wider on weak snow near the ground. Today, large avalanches are possible to trigger and avalanche danger is MODERATE.

The mountains near Cooke City got over a foot of snow in the last week equal to 1.2” of snow water equivalent (SWE). This is a small load on a snowpack that lacks widespread buried weak layers. The primary avalanche concern is fresh drifts formed by recent wind which can break under the weight of a skier or rider (Dave’s video from Wednesday, snowmobile triggered avalanche on Crown Butte last Thursday). Slopes with a shallower snowpack are less common, but are where you might find weaker, sugary snow below a slab (skier on town hill got a large collapse yesterday). The avalanche danger is MODERATE near Cooke City. 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.

TOMORROW!!! 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

On Friday a snowmobiler was killed in an avalanche in central Idaho (preliminary report from S.A.C.), and yesterday in southeast Idaho a snowmobiler was killed in an avalanche. This was the 23rd person killed by an avalanche this month in the U.S., and 30th this winter (News Release).