It's easy to trigger avalanches right now. Conditions are expected to deteriorate further before Christmas. Play safe.
Confidence
Fair - Forecast snowfall amounts are uncertain
Weather Forecast
Expect moderate snowfall on Tuesday (10-25cm) with moderate to strong south-westerly winds and freezing level around 500m. A cooler northwest flow should bring light snow or flurries on Wednesday and Thursday.
Avalanche Summary
Numerous storm slabs up to size 2.5 were triggered naturally, by skiers (including remote skier triggering) and by explosives on Sunday. Many were on lee east- to north-facing slopes, but there were some reports from all aspects at treeline and above.
Snowpack Summary
Anywhere from 20-90 cm of storm snow has built up and been shifted by winds, creating slabs above a touchy layer of large surface hoar crystals. Below around 2100m, this surface hoar sits on a hard rain crust. Above 2100m the surface hoar sits on well settled and faceted snow. This interface is highly reactive (see avalanche summary). A thick rain crust with facets from early November is buried over 1 m down and may still be reactive in isolated areas.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.