Strong wind from variable directions have set up a complicated pattern of wind-affected slopes in exposed areas.
Weather Forecast
MONDAY NIGHT: Mostly clear skies, moderate northwest winds, freezing level below valley bottom.TUESDAY: Mix of sun and clouds, moderate northwest winds, alpine temperature -10 C, freezing level below valley bottom.WEDNESDAY: Mix of sun and clouds, moderate to strong west winds, alpine temperature -10 C, freezing level below valley bottom.THURSDAY: Cloudy with light snowfall, strong southwest winds, alpine temperature -5 C, freezing level rising to 1500 m.
Avalanche Summary
No new avalanches were observed on Monday. Several loose dry avalanches and a few small (size 1) storm slab avalanches were triggered (ski cut) in this region on Sunday.
Snowpack Summary
The upper snowpack consists of hard wind slabs on north aspects, scoured and a shallower snowpack on south aspects, and a mixed bag of lower density snow in more sheltered areas. In total, 60-90 cm of December snow has formed a slab that sits on a persistent weak layer of facets (sugary snow) that formed during the dry weather in early December. This layer is most likely to be triggered on steep features where the underlying ground cover is smooth, areas where the snowpack depths are variable, or on large convex features.The lower snowpack has a weak structure composed primarily of facets over a crust on the ground. It is very likely that an avalanche triggered on the persistent slab would step down to the lower facets, resulting in a full depth avalanche.
Problems
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.
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.