Triggering avalanches is possible on slopes that have more than 30 cm of snow above crust and surface hoar layers.
Recent snow may sit above a layer of surface hoar and/or sun crusts at alpine and treeline elevations. This problem is most concerning in eastern and northern parts of the region (e.g. the Selkirks and northern Monashees) where 20-40 cm of snow sits above this layer. Elsewhere rain crusts have modified and covered these weak layers.
SATURDAY NIGHT: Partly cloudy, light west wind, low temperatures around -15 C.
SUNDAY: Cloudy with some light flurries in the afternoon, light southwest wind, high temperatures around -10 C.
MONDAY: Cloudy with up to 5 cm of new snow by the morning, light southwest wind, high temperatures around -8 C.
TUESDAY: Light flurries with 5-10 cm of snow, moderate southwest wind, high temperatures around -6 C.
Over the past few days there have been a few reports of small avalanches above the recently buried surface hoar and crust layers. These include several dry loose avalanches in steep terrain and a few size 1 skier triggered avalanches in the Selkirks. The skier triggered avalanches were 30-40 cm thick (see the photo in this MIN report). While these avalanches have limited destructive potential, we anticipate this developing into a more concerning problem when more snow arrives.
The storm earlier this week delivered a complex mix of snow, rain, and freezing rain. As a result the upper snow is highly variable. Several crusts have been reported including a widespread rain crust at lower elevations. In western and southern parts of the regions (e.g. the Monashees and Revelstoke area), this crust has been reported to extend into the alpine, with just a dusting of snow above the crust. Further east and north, temperatures remained colder during the storm and 20-40 cm of low density snow sits on the surface.
The primary concern right now is areas where this recent snow buried a widespread layer of surface hoar and/or sun crusts. This is most likely a problem in areas where 30+ cm of snow has fallen on this layer and less of a problem in areas with rain crusts near the surface. Overall, we suspect the most likely spot to find a slab above this weak layer is at treeline (and south-facing alpine) terrain in northern and eastern parts of the region.
Down near the ground remains a thick rain crust with sugary facets above and below from early November. While we have not seen recent avalanches on this layer, it produces occasional hard results in snowpack tests. It could be reactive to human triggers on shallow rocky slopes in the alpine or alpine-like features at treeline.
