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 (5-20cm) with moderate to strong south-westerly winds and freezing level around 1200m. A cooler northwest flow may bring light snow or flurries on Wednesday and Thursday.
Avalanche Summary
On Sunday, several size 2-2.5 naturally-triggered avalanches were reported. Storm slabs were also triggered by explosives and a skier. Both failed on buried surface hoar.
Snowpack Summary
Anywhere from 20-60cm of recent storm snow overlies a touchy layer of buried surface hoar, which sits on a crust below about 2100m. Winds from the north-west through south-west have created wind slabs, which are very reactive where they overlie the buried surface hoar. A lower layer of surface hoar is also reactive at the northern end of the range, buried down about 40cm. A hard rain crust with facets from early November is buried over 1 m down and is still reactive to light loads in some locations.
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.