A deeply buried weak layer remains a concern, especially on steep north facing slopes in the alpine.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
The first of two weekend weather systems is expected to reach the interior on Friday. Thursday may see light scattered flurries and freezing levels should be around 1000m with light to moderate alpine winds from the SW. The South Columbia region can expect 5-10mm on Friday with freezing levels around 1000m and moderate alpine winds from the SW. On Saturday freezing levels will rise to around 1500m and alpine winds are expected to be moderate from the west. Light scattered precipitation is expected on Saturday. The models currently have the second storm system reaching the interior early Sunday.
Avalanche Summary
No new avalanches have been reported since Sunday. On Sunday, explosive control produced avalanches to size 2.5. These occurred on N-SE aspects between 2200 and 2500m elevation. Slab depth varied from 30 to 90cm. On Saturday, isolated natural activity was reported up to size 2.5 above 2400m.
Snowpack Summary
A surface crust exists to around 2100m and is generally supportive to skiers. Above this elevation is dry storm snow which is settling out and faceting. A new layer of large surface hoar is currently forming on the snow surface. In exposed alpine terrain, strong southerly winds last week may have resulted in variable distribution of the surface snow and the formation of wind slabs. A thick rain crust with facets from early November is buried over 1 m down. Snowpack tests on this deep weak layers are showing improving results, but in some locations these layers are still reactive and has the potential to release large slab avalanches.
Problems
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.