Deep persistent weak layers at the base of the snowpack are becoming less likely to trigger, but the consequences remain high. A conservative approach to terrain selection is still recommended.
Confidence
Moderate - Freezing levels are uncertain
Weather Forecast
Freezing levels and alpine temperatures are difficult to forecast in the coming days with mild temperatures and temperature inversions dominating the weather pattern this week.WEDNESDAY NIGHT - Mainly cloudy with isolated flurries / southwest winds, 40-60 km/h / alpine low temperature near -4THURSDAY - Mainly cloudy with isolated flurries / southwest winds,30-40 km/h / alpine high temperature near -3 / Freezing level 1500 m FRIDAY - Cloudy with sunny periods / southwest winds, 10-20 km/h / alpine high temperature near +2 / freezing level 1400 m / alpine temperature inversionSATURDAY - A mix of sun and cloud / southwest winds, 10-20 km/h / alpine high temperature near +3 / freezing level 3000 m / alpine temperature inversion
Avalanche Summary
No new avalanches have been reported in the region since Saturday.On Saturday a size 2.5 explosives triggered wind slab was reported on a southeast aspect at 2000m. On Friday an explosives triggered deep persistent slab size 2.5 was reported on an east aspect at 2100m
Snowpack Summary
20-30 cm of storm snow has fallen in the region since late last week. The snow fell with strong southwest winds and sits on previous hard wind slabs, a scoured and shallow snowpack on exposed ridges, and soft snow in sheltered areas.Below 1200 m, expect to find a crust at or near the snow surface.Large variability in snow depths still exists in the region, ranging from almost no snow to nearly 200 cm in some areas. For average snowpack areas, expect to find weak and sugary faceted snow around 50 to 100 cm deep, which extend to the ground. This weak bottom half of the snowpack has been the culprit for large avalanches in the region over the past few weeks.
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.