Good Morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Tuesday, April 1 at 7:30 a.m. Montana Fish, Wildlife and Parks, Recreation Trails Grant sponsors today’s advisory. This advisory does not apply to operating ski areas.
Winds have been blowing light out of the west to southwest at 10-20 mph. Skies are clear this morning with mountain temperatures in the low teens. There is no new snow to report. Today will be sunny with winds remaining light and temperatures reaching the mid-thirties. Clouds will stream in tonight, but no new snow is expected.
Bridger Range Gallatin Range Madison Range Cooke City Lionhead area near West Yellowstone
This winter a common theme has emerged: every time it snows we get avalanches. One and a half feet of snow fell in the mountains with strong west to northwest winds over the weekend. On Saturday, Sunday and Monday skiers triggered avalanches. Yesterday skiers triggered an avalanche on a steep slope in the Beehive/Middle Basin area (photo). The slide consisted of newly wind-loaded snow and no one was hurt. On Sunday two skiers were caught in a slide as they skinned uphill in the Frazier Basin area of the northern Bridger Range. They triggered a wind slab which tumbled them 200-300 feet downhill. Luckily they ended up unburied and uninjured. On Saturday a skier triggered a few 1-2 foot deep slabs of non-wind-loaded snow south of Cooke City.
Other than avalanches in new snow and on wind-loaded slopes, the snowpack’s only other worry are facets at the ground (a.k.a. depth hoar). This deeply buried layer can avalanche (video of the garbage snow at the ground). Skiers noted a large slide on Mount Blackmore on Saturday on this layer (photo). All of our ranges have some slopes with depth hoar and Eric found some on Mount Ellis on Saturday. Triggering deep slab avalanches is difficult because our weight only affects the top 3-4 feet of the snowpack when this layer is buried 7-12 feet deep. Triggering a slide requires a recipe of being unlucky and finding an area of thinner snow where a person could collapse the depth hoar and have it propagate underneath the deepest snow. We are wary of this and have basically opted out of skiing a lot of steep terrain. If you are an avid skier and snowmobiler and have made it this far in the season without an incident, now is not the time to ramp up your ambitions. Continue to be conservative because the snowpack is still avalanching and surprising people.
I do not expect natural avalanche activity today, but human-triggered slides are a strong possibility. For this reason, the avalanche danger throughout southwest Montana is rated MODERATE, and that’s no April Fools.
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.
I 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.