Regions
Kootenay Boundary.
Weather Forecast
Friday: Cloudy but dry, with freezing levels in valley bottoms and moderate to strong westerly winds. Saturday: 5-15cm of accumulation expected with freezing levels remaining in valley bottoms, and strong southwesterly winds. Sunday: Unsettled conditions with light snowfall, light to moderate southwesterly winds, and freezing levels in valley bottoms.
Avalanche Summary
Recent observations include isolated small human-triggered wind slab avalanches near ridgecrests. One Size 2 slab avalanche was triggered by wind-loading and stepped down mid-slope to possibly the early January interface down 30cm. Loose surface snow is also sluffing readily in steep terrain.
Snowpack Summary
Recent light amounts dry snow has maintained the snow supply for fresh wind slab development and cornice growth. Surface condition in wind-exposed areas is highly variable with scoured areas, sastrugi, and pockets of fresh hard and soft wind slabs. Cold temperatures are promoting surface faceting, and a new batch of surface hoar is growing in sheltered areas. A thin melt/freeze crust can be found in the upper snowpack as high as 1900m, and some areas are reporting surface hoar buried early-January now down 10-30cm. The late-December interface is now down 30-60cm and producing moderate to hard resistant snowpack test results. The mid-December surface hoar/facet persistent weakness, down 40-100cm, is generally producing anywhere from easy results where it's shallow to hard results where it's deeper. But recent tests on a north facing treeline slope produced easy results where the surface hoar was found down 70cm, and all tests consistently show a high propensity to propagate fractures. Recent whumpfing suggests basal facets remain concern in shallow snowpack areas especially with heavy triggers in thin spots, and weaknesses in the slab above create the potential for step-down avalanches.
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.