New snow accompanied by strong southwest wind will lead to a widespread avalanche cycle on Thursday.
A layer of weak facets (sugary snow) can be found down 100-150 cm over a crust that formed in early December. There have been reports of natural and human-triggered avalanches on this layer during the last storm in areas where the overlying slab is shallower.
Reactive storm slabs will build with warmer temperatures, new snow, and wind loading.
Continued snow through the Christmas holidays. Expect some heavier snowfall amounts Thursday with the passing cold front.
Wednesday Night: 5- 20 cm of new snow accompanied by strong ridgetop wind from the southwest. Treeline temperatures near -5 and freezing levels 900 m.
Thursday: New snow throughout the day, with 15-25 cm accumulation. Strong ridgetop wind from the southwest. Treeline temperatures near -2 and freezing levels 1100 m. Potential for heavy amounts again Thursday night.
Friday: Flurries with new snow 5-10 cm with moderate to strong southwest wind. Treeline temperatures near -5 and freezing levels valley bottom.
Saturday: Mostly cloudy with some flurries 5-10 cm. Gusty ridgetop winds from the South and temperatures dropping to -12 with freezing levels valley bottom.
On Wednesday, avalanche control using explosives showed a few slab avalanches up to size 2 failing in the recent storm snow.
Natural avalanche activity will be likely through the forecast period with new storm snow and wind loading. .
New snow and wind will likely build reactive storm slabs through Friday. This new snow will bury older wind slabs from last weekend's storm.
Below the new snow exists a well-consolidated upper snowpack which overlies a substantial crust that formed in early December. This crust is approximately 90-150 cm below the surface, 20 cm thick on average, and is present across all aspects to at least 2400 m. A layer of weak facets (sugary snow) has been reported above this crust. Snowpack tests are generally showing hard results on this interface.
The lower snowpack consists of a variety of early-season crusts and mainly moist snow. Snowpack depths range from 100-200 cm at treeline elevations and taper quickly below 1800 m.
