Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain on Friday
Weather Forecast
A westerly flow dominates the next 3 days. A number of weather systems are lined up to bring varying amounts of precipitation and wind to the interior regions.Thursday: Light snowfall, Alpine temperatures -9, light to moderate west winds.Friday: Light snowfall, alpine temperatures -10, winds moderate west.Saturday: Light to locally moderate precipitation, alpine temperatures -6, freezing level rising to 1100m. Winds moderate to strong from the west.
Avalanche Summary
There have been no reports of avalanche activity in the past two days. However professional operators in the area are still concerned about the deeply buried October facet/crust layer. Although unlikely, given enough load and/or hitting the sweet spot i.e. thin area, it may be possible to trigger this layer resulting in a large and destructive avalanche.
Snowpack Summary
Up to 50cm of recent new snow has been redistributed by moderate to strong winds from a variety of aspects creating new wind slabs at the tree line elevation and above. This snow lies on top of old wind slabs, a buried rain crust that exists below 1600m and a surface hoar or facet layer that is down 100-150cm deep. Snowpack depths vary, but in general 175 cm of snow can be found at treeline, with 125-300 cm in the alpine. In some places we're still dealing with a relatively thin snowpack (thanks to a windy early season). The basal facet/crust combo (weak sugary snow above and below a crust) near the ground was active in an avalanche cycle last Thursday and Friday. This weakness may be difficult to trigger but if triggered, will result in very large, destructive avalanches.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.