Strong winds will continue building fresh wind slabs while an alpine freezing level may promote instability at higher elevations on Sunday
Confidence
Moderate - Freezing levels are uncertain on Sunday
Weather Forecast
Sunday: A mix of sun and cloud. Winds strong from the southwest. Freezing level to 1300 metres with alpine temperatures to -3. Possible temperature inversion bringing alpine temperatures to above freezing.Monday: Mainly cloudy. Winds moderate to strong from the west. Freezing level to valley bottom with alpine temperatures of -8Tuesday: A mix of sun and cloud with isolated flurries and a possible 5cm of new snow. Winds light from the northeast. Alpine temperatures of -13.
Avalanche Summary
No new avalanches have been reported. The main concern continues to be the possibility of triggering the weak faceted layers deeper in the snowpack. Ongoing winds have also been observed creating thin fresh slabs reactive to human triggering at upper elevations.
Snowpack Summary
Up to 10 cm of low density snow has been undergoing wind redistribution over the past couple of days, joining previous hard, wind-affected surfaces and forming thin layers of wind slab in lee terrain at higher elevations. Below 1500 metres you may find an isolated thin breakable rain crust about 1 cm thick. In the Elk Valley north area near Crown Mountain on Tuesday the height of snow was 90 cm with foot penetration of 80 cm; or almost to ground. Some solar exposed terrain in the alpine may have a thin sun-crust about 3 cm thick, and this may have a few cm of light dry snow above . The snowpack is quite variable throughout the region. In deeper snowpack 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. In these areas, winds have formed isolated hard slabs above weak facets and created the potential for large persistent 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.
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.