The alpine danger rating is based on localized snowfall amounts and strong winds. If you receive less then 20 cm of snow it may be CONSIDERABLE hazard in the alpine.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Monday
Weather Forecast
A strong westerly flow is driving a series of Pacific frontal systems through the Interior regions tonight through the week. Each system will be a bit stronger bringing moderate to heavy snow amounts and strong winds.Sunday Night: Snow 5-10 cm with alpine temperatures -16 and West winds 35 km/hMonday: Snow 5-15 cm with alpine temperatures near -9 and ridgetop winds southwest 30-55 km/h.Tuesday: Snow 5-15 cm with alpine temperatures -8 and ridgetop winds 30 gusting to 75 km/h.Wednesday: Light flurries with alpine temperatures -8 and ridgetop winds 30 gusting to 65 km/h.
Avalanche Summary
No new avalanche reports on Saturday. Recent reports from Thursday indicated natural cornice and ice falls from 2300 m and above on NW and SW aspects, triggering either a small wind slab or entraining surface snow on the slopes below. With forecast strong winds and new snow fresh wind slabs may build and be triggered by light loads (skiers/ sledders).
Snowpack Summary
Up to 15 cm of storm snow sits over a plethora of old snow surfaces including stiff wind affected snow, faceted (sugary) crystals and surface hoar crystals that formed in locations sheltered from the wind. The new snow will likely have a poor bond to these surfaces. 20-40 cm below this new snow sits an older buried surface hoar layer, reported from the Dogtooth Range. This layer may me reactive with additional load. The mid-November crust is buried down around 70-90 cm and test results have been variable from sudden failures to no results. In shallower snowpack areas reports indicate that the bond to the crust is weakening. Tracking and monitoring this potentially weak interface is crucial especially as we move forward into this snowy period where the snowpack will see more load.
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.