A persistent weak layer of surface hoar, facets and a crust is buried 30-60 cm down. This avalanche problem is less obvious and harder to predict, so conservative terrain choices are best.
Moderate to strong westerly wind will redistribute the recent snow and form fresh wind slabs in lee terrain in the alpine and at exposed treeline. Wind slabs will particularly be reactive anywhere they overlie surface hoar that was reported to be widespread in many sheltered areas.
Loose-dry avalanches are likely in steep terrain features.
30-60 cm sits above a buried weak interface that consists of surface hoar, facets, and/ or a crust. Forecast snow and strong wind may create enough cohesion and load to these weak layers resulting in a reactive persistent slab problem just waiting for a skier or rider to trigger.
Friday: Cloudy with isolated flurries. Alpine temperatures near -6 and light to moderate wind from the west-northwest. Freezing levels at valley bottom.
Saturday: Snow 10-15 cm. Alpine temperatures near -10 and ridgetop wind moderate to strong from the northeast.
Sunday: Mix of sun and cloud. Alpine temperatures falling to a low of -21 and a high of -14. Ridgetop wind light from the northeast.
No new reports on Thursday.
On Tuesday, reports of a widespread loose dry avalanche cycle occurred in the Babine region. These avalanches were up to size 2 and ran in steep terrain on all aspects and elevations. Wind slabs were also reactive to skier triggers up to size 1 on southwest aspects in the alpine.
With additional snow and wind, persistent slabs and wind slabs may be reactive to skier and rider triggering on Friday.
Up to 15 cm of new snow fell by Thursday afternoon bringing 20-40 cm of accumulative storm snow from the past week over a variety of old snow surfaces. These old surfaces include surface hoar in locations sheltered from the wind at all elevations, surface facets, and stiff wind affected snow. On solar aspects, a buried sun crust can be found and a thick crust exists near the surface below 1000 m. Additional snow and wind combined with cohesion may stress these potentially weak interfaces, creating the persistent slab problem.
The lower snowpack has two decomposing crust layers. The upper crust is 70-140 cm deep and continues to show occasional hard sudden results in snow pits. The deeper crust at the bottom of the snowpack is more prevalent in shallow snowpack ranges. These deep persistent layers seem to be dormant under the current conditions, but shallow rocky slopes should still be carefully assessed and approached with caution.
