Regions
Kootenay Boundary.
New snow and wind are forming small touchy slabs above a widespread layer of surface hoar. Watch for terrain traps that could magnify the consequences of getting surprised by a small slide
Confidence
Good - Forecast snowfall amounts are uncertain
Weather Forecast
Synopsis: The next strong front is forecast to move across the province on Sunday before a ridge of high pressure builds that looks to last for several days. Saturday: Snow starting in the evening with accumulations of up to 20cm around Kootenay Pass, moderate south westerly winds and freezing level at valley bottom. Sunday: Cloudy with flurries and moderate westerly winds. Monday: Mainly cloud with moderate westerly winds.
Avalanche Summary
Several small avalanches were reported to have released in windload features on Friday. Recent avalanche reports have described large avalanches ranging from size 2.5 to 3 releasing on persistent weak layers deep in the snowpack. Several of these avalanche were remotely triggered by ski touring groups from distances as far as 100m.
Snowpack Summary
Friday's snowfall buried a layer of large surface hoar or facets. In many places these week crystals sit above a thin crust which can be found up to about 1900m on north aspects and all the way to ridgeline on south aspects. While this layer is developing our main concern continues to be deeper crust/surface hoar combo buried in mid-December. This weak layer can be found 60-120cm down and still has the potential to be triggered by people. Near the base of the snowpack the facet/crust layer from November has mostly been dormant, however, isolated recent activity in the Bonnington Range suggests that this layer may still be reactive in isolated terrain.
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.