Regions
Kootenay Boundary.
Confidence
Fair - Intensity of incoming weather is uncertain
Weather Forecast
Tuesday: Light snowfall / Strong southwest winds / Alpine temperature of about -7.0Wednesday: Moderate snowfall / Strong to extreme west winds / Alpine temperature of about -9.0 Thursday: Light amounts of new snow in the morning with clearing in the afternoon / Light west winds / Alpine temperature of about -7.0
Avalanche Summary
A few size 1 slabs have recently been reported running on the January 23rd interface. They ran 30cm deep between 1800m and 1900m on east facing terrain. With forecast weather, I would suspect a spike in new snow instabilities. With the increased load on the January 23rd interface, persistent slab avalanches are likely to increase in size and destructive potential.
Snowpack Summary
Light amounts of new snow overlie hard and soft wind slabs in exposed areas, surface hoar on a variety of aspects and elevations, and a crust on previously sun-exposed slopes. About 30-40cm below the surface, an interface of surface hoar, facets or sun crust buried on Jan 23 seems to be gaining strength in some areas. Having said that, skier-triggered avalanches are still occurring, and I would continue to be cautious about this weakness as the overlying slab continues to develop over the next few days.The snowpack below this is generally well bonded.
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.