GNFAC Avalanche Advisory for Sun Mar 19, 2017

Not the Current Advisory

Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Advisory issued on Sunday, March 19th at 7:00 a.m. Today’s advisory is sponsored by Montana State Parks and Buck Products. This advisory does not apply to operating ski areas.

Mountain Weather

At 5 a.m. the mountains near West Yellowstone and Cooke City have 1” of new snow with no new snow elsewhere. Temperatures are low to mid-30s F with southwest wind at 15-20 mph. Temperatures yesterday reached highs in the mid-40s to 50s F. Under mostly cloudy skies today, temperatures will be in the 30s F with southwest wind at 20-30 mph. This morning rain is possible below 8500’. Snow levels will drop to 7000’ this afternoon with 1-2” possible in the mountains near Bozeman and 3-5” in the southern ranges and Big Sky by tomorrow morning.

Snowpack and Avalanche Discussion

Bridger Range   Madison Range   Gallatin Range   Cooke City

Lionhead area near West Yellowstone

Above freezing temperatures yesterday led to a wet, weak snowpack on all but the highest, shadiest slopes. Near and below freezing temperatures this morning will refreeze the snow surface and lower the potential to trigger wet avalanches. A thin breakable crust may be the extent of freezing on warmer slopes, and a wet and non-cohesive snowpack lies below the refrozen surface. Relatively colder temperatures today should keep the snow frozen and stable at higher elevations. Below 8500 feet, possible rain and warmer temperatures could melt the surface crust and “unlock” the wet, weak snow below.

Wet loose avalanches are easy to trigger where the snow surface is not frozen. Move to colder aspects if fresh pinwheels and small point releases are present (photo), or if you sink past your boot top in wet snow. Rain and melt-water draining through the snowpack increases the chances for large wet slab avalanches. The forecast does not call for large amounts of rain, but avoid avalanche terrain if rain showers become heavy.

Conditions and stability can change quickly this time of year. Temperatures hit record highs yesterday and snow showers are expected today. Check out this article on spring snow avalanche problems for more travel advice and a breakdown of some things to look for.

Today, wet snow avalanches are possible and the avalanche danger is MODERATE.

Note: Cornices are large (photo) and can fail naturally or with human triggers. These monsters can break farther back than you might expect, so give them a wide berth along the ridgelines and avoid slopes directly below them.

I will issue the next advisory tomorrow morning by 7:30 a.m.  


We rely on your field observations. Send us an email with simple weather and snowpack information along the lines of what you might share with your friends: How much new snow? Was the skiing/riding any good? Did you see any avalanches or signs of instability? Was snow blowing at the ridgelines? If you have snowpit or test data we'll take that too, but this core info is super helpful! Email us at mtavalanche@gmail.com or leave a message at 406-587-6984.