Good Morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Wednesday, April 2 at 7:30 a.m. REI, in partnership with the Friends of the Avalanche Center, sponsors today’s advisory. This advisory does not apply to operating ski areas.
One to two inches fell from Big Sky to West Yellowstone and Cooke City last night. Under cloudy skies temperatures are in the mid-teens and winds are out of the southeast at 20-25 mph in the Bridger Range and 10 mph everywhere else. Scattered snow showers will drop another 1-2 inches in the southern mountains this morning. This afternoon skies will become partly cloudy, temperatures will rise into the upper thirties and winds will remain light.
Bridger Range Gallatin Range Madison Range Cooke City Lionhead area near West Yellowstone
Last night’s 1-2 inches of new snow and light winds will not adversely affect the snow stability. Since last Thursday the mountains have gotten two inches of water weight (1.5-2 feet of snow) and avalanches ensued. On Sunday in Frazier Basin skiers triggered a slide on a wind-load as they skinned up a slope. They were caught and tumbled a few hundred feet, but were ok. That same day skiers triggered an avalanche in the new snow south of Cooke City (photo), and on Monday a skier triggered a slide on the ridge between Beehive and Middle Basins near Big Sky (photo). This new snow poses the greatest avalanche threat, but it should stabilize in the next day or two.
Besides instability with the new snow, our second avalanche concern is found near the ground. Large sugary grains of facets (depth hoar) are occasionally avalanching in big, deep slides involving the entire season’s snowpack (photo). The depth hoar is found throughout our advisory area but it is very difficult to trigger and unreliable to test in a snowpit (blog post). It’s a sleeping dragon. I found it yesterday in Bacon Rind and Eric tested it on Mt. Ellis on Saturday. A person could get unlucky and trigger a deep slab avalanche from an adjacent, thinner area of the snowpack. Until this layer shows some solid evidence of stabilizing (for example: water runs through it and it refreezes) I am not entirely trusting it. Deep slab avalanches are a low probability, high consequence type of problem.
Today the avalanche danger is rated MODERATE on all slopes throughout southwest Montana.
Cornices: Cornices are growing at a fast rate and are getting quite enormous this season. They can break with a passing skier and deserve a wide berth. A falling cornice can also be a very good trigger for deep slab avalanches.
Mark will issue the next advisory tomorrow morning at 7:30 a.m. If you have any snowpack or avalanche observations drop us a line at mtavalanche@gmail.com or call us at 587-6984.
Our last daily avalanche advisory will be this Sunday, April 6th. If conditions warrant we will issue intermittent advisories the following week.