New snow and wind has reactivated our wind slab problem at higher elevations. Seek out sheltered areas holding low density snow for the best and safest skiing and riding.
A bit of new snow has supplied forecast winds with the building blocks of a fresh wind slab problem. Consistently elevated winds should maintain slab formation throughout the day on Saturday. Expect this problem to increase with elevation and be especially pronounced in the immediate lee of exposed terrain features.
Our weak basal snowpack has produced sporadic very large avalanches - both natural and human triggered - in the past couple of weeks. More details here and here. It remains important to consider the potential for deep avalanches from suspect features in the region. The most likely trigger points are thin rocky areas near ridge crest. Rock outcroppings in exposed terrain should be avoided.
Friday night: Mainly cloudy with continuing isolated flurries and a trace of new snow. Moderate west winds, becoming strong at ridgetop.
Saturday: Cloudy with isolated flurries and a trace of new snow, increasing a bit overnight. Moderate southwest winds, strong at ridgetop. Alpine high temperatures around -8.
Sunday: A mix of sun and cloud with isolates flurries and up to 5 cm of new snow. Light west winds. Alpine high temperatures around -9.
Monday: Mainly sunny. Light west winds. Alpine high temperatures around -10.
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. Preliminary reports show 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 easily 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.
