Storm slabs will likely be touchy to human triggering on Friday. Especially on wind-loaded leeward slopes.
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.
Storm slabs could be reactive to human triggering on Friday, especially on leeward (wind-loaded) slopes that host thicker and stiffer slabs.
Loose-dry sluffing will likely exist on steeper wind-sheltered slopes and terrain features.
Light snow and flurries will continue in most areas as a cold northeasterly flow begins to assert itself at the surface. This will bring persistent cloudiness and continued light snowfall amounts through the Christmas weekend.
Thursday Night: New snow 5-10 cm accompanied by moderate southwest wind. Treeline temperatures -8 and freezing level at the valley bottom.
Friday: New snow 5-10 cm with strong southerly winds. Treeline temperatures near -10 and freezing levels near 800 m. Temperatures continue to drop overnight.
Saturday: Cloudy with 5-15 cm accompanied by moderate southwest wind. Treeline temperatures near -15 and freezing levels at the valley bottom.
Sunday: Cloudy with some flurries up to 5 cm. Light winds from the southwest and colder temperatures at -15.
On Thursday, numerous storm slabs were triggered by machines and explosives. The majority of them were size 2 with one size 3 reported.
Natural avalanche activity may taper on Friday but slab avalanches likely remain primed for human triggering.
30 to 50 cm of recent storm snow sits above a surface hoar interface and pockets of old wind slab. Low-density storm snow exists in wind-sheltered sheltered terrain.
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.
