Wind slab formation has been steady over the past week and the pattern continues overnight Saturday, although new accumulations should be light. Keep seeking out sheltered snow and be ready to step back from sun exposed slopes in the afternoon.
Consistent light snowfalls have been supplying steady moderate to strong winds with the building blocks of a fresh wind slab problem, and a bit more snow is on the way for Saturday night. Expect this problem to increase with elevation and be especially pronounced in the immediate lee of exposed terrain features.
Saturday night: Cloudy with flurries bringing about 5 cm of new snow. Moderate west or southwest winds.
Sunday: Diminishing cloud with isolated flurries in the morning. Light northwest winds. Alpine high temperatures around -10.
Monday: Mainly sunny. Light west winds. Alpine high temperatures around -10.
Tuesday: Sunny. Light west winds. Alpine high temperatures around -11.
Locally enhanced snowfall in the Castle area over Thursday night led to a moderate rise in avalanche activity in that part of the region of Friday. Reports showed ski cutting and explosives control yielding mainly small (size 1) dry loose releases. One natural size 1.5 storm slab was also observed, giving some indication of conditions in the range.
Over the last few days, reported avalanche activity was mainly limited to small dry loose avalanches and small wind slabs triggered with ski cutting and explosives control, however another recent large deep persistent slab is described in the following MIN report.
There was also a bigger avalanche reported in this MIN on February 9th (check out the photos, they're humbling). The very large avalanche ran on a north facing feature at 2400 m and was triggered by a snowmobile. 10 or so climbs had been made in the same area in the days leading up to this avalanche without incident.
Before the above avalanche, the last avalanche cycle to include persistent slabs was during the first weekend in February. These patterns of activity suggest our deep persistent slab problem may resurface more decisively during stormy periods but also that it can't fully be ruled out even when surface instabilities are limited.
Another variable 5-20 cm of new snow accumulated in the region over Thursday night, with the Castle area appearing to hold the most substantial amounts.
The new snow buried mainly wind-affected surfaces and aging wind slabs in exposed areas, while adding to about 10-30 cm of older settled storm snow in sheltered areas. This brings snow totals above our widespread rain crust to about 20 to a possible 50 cm, with the east slope of the region again generally holding the deeper amounts.
We have previous observations of surface hoar forming in the Elk Valley in advance of last Friday's storm (see here), meaning this weak layer is now likely about 20 cm deep in that part of the region, and possibly elsewhere as well.
A well consolidated mid-pack overlies generally weak basal facets, that may be possible to trigger in isolated shallow rocky start zones.
