Weak layers buried near the bottom of the snowpack remain a concern. A conservative approach to route selection is recommended.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
MONDAY NIGHT: Clear periods, light to moderate west winds, alpine temperature -10 CTUESDAY: Cloudy with sunny periods, Light southwest winds, alpine temperature -6 CWEDNESDAY: Mainly cloudy with isolated flurries, light southwest winds, alpine temperature -2 C, possible temperature inversionTHURSDAY: Mainly cloudy with isolated flurries, light to moderate southwest winds, alpine temperature -4 C, freezing level 1500m
Avalanche Summary
Most recent avalanche activity has been reported as an explosives controlled deep persistent slab size 2.5 release on an east aspect at 2100m on Friday and also on Saturday of a size 2.5 explosives controlled wind slab release on a southeast aspect at 2000m.
Snowpack Summary
Large variability in snow depths still exists in the region, ranging from practically no snow to almost 200 cm. Upwards of 50-60 cm of snow fell late last week above 1500 m. 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 1500 m, expect to find a hard crust at or near the snow surface.For average snowpack areas, expect to find weak and sugary faceted grains 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.