New snow is creating touchy storm slabs: It's time to rein in your terrain choices and stick to simple, low consequence terrain. Avoid all overhead hazard as well - avalanches have the potential to run to valley bottom.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
Significant snowfall through to Monday afternoon.SUNDAY: Periods of snow, accumulation 20-30cm by day's end / Light to moderate southeast wind / Alpine temperature -7MONDAY: Flurries, accumulation 10-20cm / Light to moderate southeast wind / Alpine temperature -20TUESDAY: Scattered flurries / Light southwest wind / Alpine temperature -15
Avalanche Summary
Soft slabs from the storm snow were very reactive to ski cutting and explosives control on Saturday. The size and distribution of avalanches will increase significantly by Sunday afternoon: It's time to seriously dial back the terrain use and stick to simple, low consequence terrain. The possibility of triggering the weak faceted layers deeper in the snowpack remains a concern, and storm slabs may step down to trigger larger, more destructive avalanches.
Snowpack Summary
Taking regional variations into consideration, 15-25cm of new snow typically sits on wind-affected surfaces at higher elevations. This new snow is forming touchy soft slabs on all aspects as winds have been shifting on Saturday. Below 1500 metres you may find an isolated thin breakable rain crust about 1 cm thick. The snowpack is quite variable throughout the region. In deeper areas, the snowpack appears to be well settled with isolated concerns about the mid-December facet layer buried 50-100 cm deep. In shallow snowpack areas and lower elevations, the snowpack is weak and faceted. For instance, in the Elk Valley north area near Crown Mountain last week the height of snow was 90 cm with foot penetration of 80 cm; or almost to ground. In these areas, the wind has formed isolated hard slabs above weak facets and created the potential for large persistent slab avalanches.
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.