GNFAC Avalanche Forecast for Sun Apr 11, 2021

Not the Current Forecast

Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Forecast on Sunday, April 11th at 7:15 a.m. This is our 121st and final daily forecast of the season. Today's forecast is made possible by you, the readers of our advisory, everyone that sent in observations, took an avalanche class or donated money, time or gear. Our success is directly related to community support and the Forest Service. Thank you for another great season. This forecast does not apply to operating ski areas.

Mountain Weather

Last night, 5” of snow fell in Hyalite with 2-4” near Big Sky and the Bridger Range and zero elsewhere. Temperatures are single digits to low teens F (fifteen to twenty degrees colder than yesterday morning). Overnight, wind was west to northwest at 10-20 mph with gusts of 25-35 mph. Today wind will decrease to 5-15 mph as it shifts to the north and then east. Skies will be mostly cloudy with temperatures in the 20s F. Light snow showers are possible today with 1-2” near Cooke City and maybe an inch elsewhere.

Snowpack and Avalanche Discussion

In the northern Gallatin Range, 5” of new snow equal to 0.5” of snow water equivalent (SWE) creates heightened avalanche conditions. Last night and this morning, moderate west-northwest wind formed fresh drifts that are possible to trigger. The new snow fell on hard melt-freeze crusts which will help wind slabs and loose snow avalanches slide farther and wider. Avalanches breaking deeper than the new snow are unlikely. Before you ride steep slopes carefully evaluate the stability of the new snow, and be extra cautious of wind-loaded slopes. Watch for cracking around your skis or feet on lower angle slopes as a sign the new snow can slide on steeper slopes. Avalanches are possible to trigger and the avalanche danger is MODERATE.

Near Big Sky, the Bridger Range, West Yellowstone and Cooke City the snowpack is generally stable, and avalanches are unlikely aside from small, isolated slabs of wind-drifted snow. In the Bridgers and near Big Sky 2-4” of new snow equal to 0.1-0.2” of snow water equivalent (SWE) was drifted by northwest wind into fresh slabs. Though small, these slabs are potentially hazardous in higher consequence terrain like above cliffs, rocks, trees or on firm, steep slopes. If there is any mid-day sun that makes the new snow moist, small loose snow avalanches will become possible. Prior to last night’s snow, two days of moderate-strong southwest winds formed small wind slabs along ridgelines that have become difficult to trigger. Evaluate the consequences of being caught in even a small slide before riding steep terrain. Today, the snowpack is generally stable and the avalanche danger is LOW.

We will issue spring snowpack and weather updates each Monday and Friday through April, or as needed, and we will share relevant avalanche and snowpack observations on our website and social media. 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).

Avalanche Education, Events and Announcements

Bridger Bowl is closed, and backcountry conditions exist (video). There is no avalanche mitigation or ski patrol rescue. Please stay clear of work areas, snowmobiles, chair lifts and other equipment.

See our education calendar for an up-to-date list of all local classes.

The Last Word

The weather the next few days will be similar to today, cold with light snow, then slightly warmer temperatures return next weekend. Snow will be around the mountains for a month or two and avalanches will continue.

When warm temperatures return, wet snow hazards will increase. If there are big spring snowstorms, dangerous conditions may develop for new snow avalanches and wind slabs. With either extended warming or a big storm, there is still a lingering possibility for deep avalanches breaking on weak, sugary snow near the ground. See this article for some general spring travel advice.


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