Regions
Kootenay Boundary.
Don't be fooled by the Moderate danger ratings. Buried weak layers still exist and may surprise in isolated terrain with nasty consequences.
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Thursday
Weather Forecast
Wednesday night: 10-15cm of new snow / Moderate westerly winds / Alpine temperature of -13Thursday: 10-15cm of new snow / Light to moderate westerly winds / Alpine temperature of -13Friday: 5-10cm of new snow / Light and variable winds / Alpine temperature of -9Saturday: Mix of sun and cloud / Light and variable winds / Alpine temperature of -13
Avalanche Summary
On Tuesday, a skier triggered a size 1.5 wind slab on a north-facing alpine slope in Kokanee Glacier Provincial Park. The skier went for a short ride, but was uninjured in the event. No other recent avalanches have been reported. As new snow accumulates over the next few days, fresh wind slabs should remain on your radar. More importantly, the December 15th interface will become deeper. With that, the overlying slab may settle and gain cohesion increasing the likelihood of triggering of this buried persistent weak layer.
Snowpack Summary
By Thursday morning, up to 15cm of low density snow is expected to have fallen. Moderate west winds are forecast to shift these accumulations into deeper deposits in high elevation lee terrain. The new snow overlies recently buried surface hoar, although at this point not much is known about the size or distribution of this potential weak layer.Between 30 and 75cm below the surface you'll find the December 15th interface which consists of a melt-freeze crust on steep, solar, higher elevation slopes and well-developed surface hoar which seems most pronounced in sheltered treeline terrain and below. The bond at this variable interface is of critical importance, especially in areas where the overlying slab is deep and well-consolidated.The late November crust is now buried 60-100 cm and has been producing hard, resistant results in recent snowpack tests. Beneath this crust the lower snowpack is strong and well-settled.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.