Avalanche danger is expected to remain at Considerable during the forecast cold and clear weather for the end of the year.
Weather Forecast
Gradually clearing overnight with light Northeast winds and alpine temperatures dropping down to about -16. Mostly clear and cold on Monday with light to moderate Northeast winds and alpine high temperatures around -14. Clear and cold on Tuesday with light Northwest winds. Continued clear and cold on Wednesday.
Avalanche Summary
A report from one operator on Saturday described remotely triggering several avalanches up to size 2.5 that were releasing down 45-60 cm on the buried surface hoar between 2200-2450 metres elevation. The persistent slab problem is expected to continue for the forecast period.
Snowpack Summary
5-15 cm of light dry new snow has been added to the recent storm slab. In some parts of the region a thin breakable rime crust exists between the new snow and the storm slab. The upper 40-90 cm of storm snow is slowly consolidating into a slab above a touchy surface hoar layer buried mid-December. Below 2100 m this slab sits on a thick, solid crust/ surface hoar combo and acting as a perfect sliding layer. Persistent slabs may be touchy to the weight of a skier or rider, especially in wind effected areas where the slab is stiffer. Deeper in the snowpack is a hard rain crust with facets from early November. This is buried over 1 m down and is currently unreactive but triggering from shallow rocky, unsupported terrain remains a concern.
Problems
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.
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.