Regions
Kootenay Boundary.
Maintain caution around wind slabs at higher elevations. Slabs in steep terrain and on unsupported slopes are likely to remain reactive to human triggering.
Weather Forecast
Sunday: Mainly cloudy with no new snow. Winds light from the west. Freezing level to 700 metres with alpine temperatures of -6.Monday: Flurries bringing 10-15 cm of new snow. Winds light to moderate from the southwest. Freezing level to 900 metres with alpine temperatures to -5Tuesday: Periods of snow with 20-35 cm accumulations. Winds moderate to strong from the south. Freezing level rising to 1600 metres with alpine temperatures around 0.
Avalanche Summary
No new avalanches have been reported, but Thursday's reports included a size 2 slab avalanche triggered from a heavy load of snow being moved by machinery. The avalanche ran on weak basal facets at ground level from a south aspect at around 1700m. It did take a large load to trigger this avalanche, but it may be a good indication of what a cornice failure may be capable of. Something to be kept on your radar as we transition into a warmer, wetter period next week.
Snowpack Summary
Recent cold and clear weather has promoted both faceting of surface snow as well as the growth of surface hoar that has been reported to be up to 15mm in size below treeline. A sun crust has also been reported forming on steep solar aspects. Below the surface, up to 20 cm of recent snow has been redistributed by moderate to strong winds from all directions, forming reactive wind slabs on a variety of aspects. The recent snow buried a plethora of old snow surfaces, including wind scoured surfaces and old wind slabs, widespread near surface faceting (sugary snow), surface hoar in sheltered locations, and/or a breakable sun crust on steep solar aspects. The mid-December surface hoar/ facet layer typically sits down 40-70 cm. This layer is still reactive to some snowpack tests in some areas but is currently considered to be dormant or inactive. However, once the snowpack starts to see a big change, like warming, the likelihood of triggering may increase.
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.