Hazard will likely depend on the extent of cooling and new crust formation Thursday overnight. Storm slabs are expected to remain touchy up high where the snow remains dry, especially in wind loaded terrain.
A reactive storm slab should be expected where the snow surface remains dry and crust-free at higher elevations. They will be most reactive in wind loaded terrain.
At lower elevations where the snow surface remains moist or wet, human triggered wet loose avalanches remain possible on steep slopes.
Unsettled conditions are expected for Friday with a ridge of high pressure to the south and a weak storm system approaching from the west.
Thursday night: Partly cloudy, moderate SW wind becoming strong by early morning, freezing levels may linger at around 2000-2500 m with a temperature inversion and below freezing temperatures in the valleys.
Friday: Mainly cloudy with periods of light flurries, strong SW wind, freezing levels around 1500 m.
Friday night and Saturday: Snowfall up to 25 cm, strong SW wind, freezing levels around 1500 m.
Sunday: Snowfall, moderate to strong SW wind, freezing levels around 1000 m.
On Wednesday, skiers were triggered three size 1-1.5 storm and wind slabs between 1700 and 2000 m. These slabs were 20-50 cm thick. No new avalanches were reported on Tuesday but observations were limited.
On Friday, the avalanche hazard is uncertain and will likely depend on the extent and thickness of a new surface crust. Where the skies are clear and the freezing levels drop substantially, a thick crust and lower hazard can be expected. Storm slabs will remain a concern at higher elevations, especially in wind loaded terrain.
On Thursday, freezing levels climbed into the alpine in the south of the region and to at least treeline in the north. With temperatures expected to drop on Thursday night, a widespread surface crust is expected to form. Below the new crust, 30-50 cm of recent storm snow has been settling rapidly with the mild temperatures. This snow overlies a previously wind-affected surface comprised of old hard wind slabs, sastrugi, and areas stripped back to the ground or old crusts. Snow at this interface was significantly weakened during the cold snap, which means the bond here remains in question.
The early-December crust/facet interface can typically be found down 50-150 cm but has been dormant recently and is no longer expected to be creating an avalanche problem in the region. The base of the snowpack is composed of crusts and weak faceted grains, particularly in thin snowpack areas east of the divide.
