Regions
Northwest Inland.
Weaknesses deep in the snowpack will heal much more slowly than wind slabs. Keep your guard up around big overhead terrain and in thin snowpack areas in the alpine.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Saturday: Mainly cloudy with isolated wet flurries and a trace of new snow to higher elevations. Light to moderate southwest winds. Alpine temperatures hovering around 0 as the temperature inversion persists. Cooler at lower elevations.Sunday: Cloudy with continuing light wet flurries bringing a possible 2 cm of new snow to alpine elevations. Light rain below about 1800 metres. Light to moderate south winds. Freezing level to 2300 metres with alpine temperatures around 0 to +1.Monday: A mix of sun and cloud. Moderate south winds. Freezing level to 3200 metres with alpine temperatures around +5. Cooler at valley bottom due to temperature inversion.
Avalanche Summary
No new avalanches have been reported, however it is expected that warm alpine temperatures and sunshine initiated natural activity on steep solar aspects at higher elevations on Thursday and Friday. Looking forward, expect any new snow accumulations to bond poorly with the crust and surface hoar that form our current snow surface.
Snowpack Summary
Average snowpack depths now total 80-140 cm at treeline elevations and up to 160 cm in the alpine. (Depths of up to 210 cm have been reported from the Howsons.) Solar and temperature crusts are expected to have formed on the wind-affected surface at higher elevations on Thursday. Below the surface, Approximately 30-50 cm of storm snow now overlies two crusts that were buried near the end of November. These crusts are widespread and extend into the alpine. Although snowpack tests have previously shown hard results at these crust interfaces, more recent observations have been limited. Below these crusts, a well settled midpack overlies the late October crust near the base of the snowpack. This "crust/facet combo" layer is widespread and has been reactive to rider and remote triggers. It also continues to produce sudden snowpack test results.
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.