Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Tuesday, March 29, at 6:45 AM. Today’s advisory is sponsored by Grizzly Outfitters and the Friends of the Avalanche Center. This advisory does not apply to operating ski areas.
Last night, scattered showers dropped a trace to 1”of snow in the northern mountains and 1-2” in the south. This morning temperatures are in the high teens and winds are east to northeast at 10-20 mph, gusting to 30 mph at Lionhead and Cooke City. Today will be cloudy, scattered snow will continue, and temperatures will rise into the upper 20s with east winds at 15-30 mph. The mountains will get 2-4” today with Cooke City poised for 6-8” before the storm tapers off this afternoon.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
We awoke yesterday morning to 6-10” of snow in the mountains with moderate west to northwest winds. Yesterday, a large natural avalanche released in the northern Bridger Range on Sacajawea Peak in Airplane Bowl (photo) and ski patrols easily triggered soft slabs of windblown snow that broke up to 2 feet deep. Last night’s couple of inches and east winds will chew back cornices (good), but they’ll load the west side of the ranges (bad).
The avalanche on Sacajawea Peak concerns me. It looks like it was 500 feet wide and a few feet thick. This is evidence of a prominent weak layer: likely facets but possibly graupel. We have not seen widespread evidence of instability, but avalanche activity tops all other observations and snowpit tests. With wind-loading, more snow and a large avalanche that’s a bit of a surprise, I recommend notching back ambitions today. Avalanches like this are a gift because they make us pause and reassess. Although the avalanche occurred in the Bridger Range, its cautionary message is region wide: large avalanches are possible. Close to an inch of snow water equivalency fell in the last 36 hours which is a substantial load. In the southern mountains a layer of facets is buried 2-3 feet deep and avalanches occurred in the northern Madison Range (photo) and outside Cooke City (photo) on Saturday.
West to north winds yesterday and east winds last night will load many slopes in uncommon patterns creating a CONSIDERABLE avalanche danger on wind-loaded slopes steeper than 35 degrees. All other slopes have a MODERATE avalanche danger.
I will issue the next advisory tomorrow morning by 7:30 a.m. If you have any snowpack or avalanche observations to share, drop us a line at mtavalanche@gmail.com or leave a message at 587-6984.