Triggering avalanches remains possible at upper elevations where 20-40 cm of snow is gradually settling above weak layers.
20-40 cm of 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). Elsewhere rain crusts have modified and covered these weak layers.
A weak frontal system arrives on Tuesday.
SUNDAY NIGHT: A trace of snow overnight, moderate southwest wind, low temperatures around -10 C.
MONDAY: Cloudy with some light flurries, moderate southwest wind, high temperatures around -8 C.
TUESDAY: Flurries throughout the day bring 5-15 cm of new snow, strong south wind, high temperatures around -6 C.
WEDNESDAY: Another 10 cm overnight then clearing in the afternoon, 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, some small naturally triggered slab avalanches on solar aspects, 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.
Last week's storm left a wide variety of surface conditions. 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 has buried layer of surface hoar and/or sun crusts. This is most likely a problem in areas where 30+ cm of snow sits above 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.
A buried rain crust can be found in the lower snowpack (50-150 cm deep) with some reports of weak snow around this crust. While we have not seen recent avalanches on this layer, it continues to produce occasional results in snowpack tests. It may be reactive to human triggers on shallow rocky slopes in the alpine or alpine-like features at treeline.
