Regions
Kootenay Boundary.
A dramatic shift in the weather will increase avalanche hazard fairly rapidly once it starts to snow. If you see anything of interest, remember to let us know by submitting an observation using the CAC Mobile app.
Weather Forecast
The prolonged dry spell finally ends on Monday with some cold, low density snow.Sunday: Dry with increasing cloud cover. Winds light from the W. Treeline temperatures around -14C.Monday: Models are currently showing 2-5 mm precipitation, which could give 5-10 cm new snow given the cold temps. Ridgetop winds gusting to around 40 km/h. Treeline temperatures around -12C.Tuesday: 10-15 cm new snow expected. Ridgetop winds around 60 km/h. Treeline temperatures around -5C.
Avalanche Summary
A size 2 wind slab avalanche was reported from a NW aspect at 2000 m on Friday. On Thursday, there were several reports of skier triggered loose dry avalanches and a couple of slab avalanches size 1.
Snowpack Summary
Recent strong E winds have scoured windward alpine faces and created 10-30 cm thick hard windslabs on lee and cross-loaded features in the alpine and at treeline. The windslab problem is sticking around longer than usual because of the prolonged cold temperatures and also because they are sitting on a widespread surface hoar layer (and/or a suncrust on S facing slopes). Hence, the windslabs or loose snow in sheltered terrain are still reactive to skier traffic. The mid snowpack is strong and supportive. Deeper persistent layers have become unlikely to trigger, although large and destructive avalanches are still possible in isolated terrain with the right input such as a cornice fall or a heavy load over a thin spot in steep terrain. At the surface of the snowpack, a new surface hoar layer is growing in sheltered areas and surface facetting continues.
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.