Confidence
Fair - Due to variable snopack conditions
Weather Forecast
Wednesday: Flurries in the morning with moderate northerly winds. Alpine temperatures around -12C. Thursday: Dry. Winds becoming westerly. Remaining cold, but an inversion could locally elevate alpine temperatures by a few degrees. Friday: Flurries. Moderate NW winds. Alpine temperatures around -10C.
Avalanche Summary
We have had reports of shallow slab avalanches affecting the top 20 cm of the snowpack, running on the mid-December surface hoar layer. Although these shallow slides (to size 1.5) do not have much mass, they were reported as running "fast and far". They were reported from the Harvey Pass area at 1800-2000m on a north aspect.
Snowpack Summary
Recent strong winds have flipped from southerly to northerly and back to southerly. As a result, a highly variable snowpack exists in the alpine and exposed areas at treeline. Some areas are completely scoured; some have fresh layers of hard wind slabs. In more sheltered locations, a buried layer of surface hoar lies approximately 20 cm below the snow surface. A well settled mid pack bridges over the basal weaknesses at the ground. The crust/facet combo still exists at the ground. This layer was responsible for some large releases earlier on in the season. However, there hasn't been any activity on this layer since early December and confidence is growing that it has gained strength.
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.