A powerful storm has changed avalanche conditions. The snowpack will need some time to adapt.
50 cm or more may accumulate by the end of Thursday morning, forming new storm and wind slabs. An avalanche cycle may occur during the peak of the storm and slabs will likely remain reactive to riders over the course of the day. Wind slabs will likely continue to build even once the snow stops falling.
WEDNESDAY NIGHT: Cloudy with snowfall, accumulation 20 to 30 cm, 60 km/h southwest wind, alpine temperature -3 C, freezing level rising to 1000 m.
THURSDAY: Cloudy with snowfall, accumulation 10 to 20 cm, 50 km/h west wind, alpine temperature -4 C, freezing level 1000 m.
FRIDAY: Cloudy with snowfall, accumulation 5 cm, 60 km/h southwest wind, alpine temperature -2 C, freezing level 800 m.
SATURDAY: Mix of sun and cloud with no precipitation, 60 km/h southwest wind, alpine temperature 0 C, freezing level 2300 m.
A few wind slab avalanches were triggered naturally and by skiers on Tuesday. They were 20 to 40 cm deep and on southeast to north aspects. In the north, a persistent slab that released on the faceted grains described in the snowpack summary was triggered by a cornice fall.
A natural avalanche cycle may occur Wednesday night into Thursday as snow rapidly accumulates.
We are in the midst of a strong storm that may deposit over 50 cm of snow by Thursday afternoon. Storm slabs will rapidly form in areas sheltered from the wind. The snow may be particularly reactive where it sits on small surface hoar crystals. The snow is falling with strong southwest wind, so wind slabs will form in exposed terrain at higher elevations. Below around 800 to 1000 m, the snow may switch to rain on Thursday.
Two weak layers may be found. A layer of surface hoar that formed mid-January may be found around 80 cm deep, particularly around Bear Pass and in the north of the region. A layer of sugary facetted grains may be found about 80 to 130 cm deep, which formed during the cold spell in late December to early January. To date, these layers appear to be most problematic in the northern half of the region.
The remainder of the snowpack is mostly strong in the south of the region. In the north of the region, the base of the snowpack consists of faceted grains around a melt-freeze crust, which is currently dormant.
