Confidence
Fair - Timing of incoming weather is uncertain on Friday
Weather Forecast
Wednesday: Cloudy with a few snowflakes. Cold (around -20C). Moderate to strong westerly winds. Freezing level valley floor.Thursday: Light snow possible at times. Remaining cold. Friday: The next frontal system is due to hit the region late in the day, bringing moderate-heavy snow, rising temperatures and gusty winds. Freezing level climbing near 1500m by the evening.
Avalanche Summary
Recent reports include a few reluctant slope cut size 1 soft slabs on steep, convex, unsupported features. They had limited propagation and did not run far. Low density storm snow is sluffing readily in steep terrain. In some cases they're entraining considerable mass and reaching up to size 2.
Snowpack Summary
5-10cm additional snow brings storm totals to about 40-50cm. This sits over a variety of surfaces (facets, surface hoar in sheltered areas, soft slabs, hard slabs, wind crust, and a melt-freeze crust below treeline). So far the storm snow has remained relatively cohesionless and has only been reacting as a very soft slab in a few areas. However, I'd expect wind slabs to be developing now in open areas.A surface hoar layer buried in mid-December is gaining strength, but professionals are still treating it with caution, as the consequences of an avalanche on this layer would be high. It's now down about 130cm in the snowpack.
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.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.