Wind slabs at upper elevations remain a concern. Seek out soft snow sheltered from recent winds.
Winds have drifted recent snow into slabs on leeward features that may be possible to trigger. Winds have changed in strength and direction from extreme out of the southwest to moderate out of the northwest, creating a tricky loading pattern. Areas where wind slabs have formed overlap with areas where cornices may be reaching their breaking point.
A layer of weak, sugary facets persists at the bottom of the snowpack. Areas where the snowpack transitions from thick to thin may still harbor this deep persistent slab problem, like shallow, rocky alpine start zones. Easier-to-trigger wind slab avalanches or cornice falls could step down to this deeper layer, resulting in very large avalanches.
Wednesday night: Cloudy, isolated flurries with a trace of snow, light to moderate northwest winds, alpine temperature -11 C.
Thursday: Mostly cloudy, scattered flurries with a trace of snow, light northwest winds, alpine high temperature -6 C.
Friday: Partly cloudy, isolated flurries with a trace of snow, light variable winds, alpine high temperature -5 C.
Saturday: Cloudy, 5-15 cm of snow, light northeast winds, alpine high temperature -5 C.
Since the weekend storm, there have been several reports of failing cornices and small wind slabs. See this MIN report for a helpful illustration. Explosive triggers have also released several large avalanches breaking on deeply buried weak layers on a variety of aspects above 2200 m. This activity is a good reminder that this layer remains a problem in the region. Easier-to-trigger wind slab avalanches or cornice fall may have the potential to step-down to this layer.
During the weekend storm, numerous size 2-3.5 slab avalanches released naturally. A few were thought to have stepped down to deeper layers. These avalanches primarily occurred on leeward aspects at treeline and alpine elevations. Below tree line, wet loose avalanches ran naturally during the warm temperatures on Saturday.
Incremental snow and wind is adding to previous wind-loading in the alpine and at treeline. Where the snow is being drifted and stiffened by wind, human-triggered avalanches may be possible. Cornices are large and looming and may be reaching their breaking point.
40-60 cm of snow fell during the weekend storm above 1900 m. Extreme winds originating from the southwest and shifting to the northwest created a tricky loading pattern at treeline and above and accelerated cornice growth.
Below 1900 m, 10-20 cm snow may cover a crust that formed during the storm from warm temperatures and rain. The snow above this crust is well-bonded and gaining strength.
A weak layer of surface hoar may still be found about 90 cm deep around Golden and Kimberley, 50 cm deep around Invermere, and 130 cm deep along Kootenay Lake. As usual for the Purcells, the base of the snowpack contains basal facets. It remains possible to trigger these deep weak layers in shallow rocky start zones or from a heavy trigger such as a cornice fall.
