Avalanche danger will rise as a soft slab forms above a widespread layer of surface hoar and a crust. Danger may be lower than forecast in areas that that receive less snow.
Confidence
Fair - Intensity of incoming weather systems is uncertain
Weather Forecast
A frontal system will bring another 10 to 15cm of new snowfall to the region overnight on Monday with 5 to 10cm expected for Tuesday. A ridge of high pressure building over the province Wednesday will bring dry conditions. Winds will belight to moderate from the west to southwest. Freezing levels will remain at valley bottom until at least Tuesday.
Avalanche Summary
There was a widespread avalanche cycle earlier in the week that produced numerous large to very large avalanches. Natural activity has now eased, but the present of persistent layers in snow pack suggest that it may be possible for humans to trigger an avalanche. Forecast snow above a crust and SH means a reactive soft slab is likely to form.
Snowpack Summary
Up to 25 cm of new snow overlies a variety of old surfaces. A crust formed last week at most elevations. In some places it was breakable in others it was supportive. A thin widespread layer of surface hoar lies above this crust. At the highest elevations the old surface was widely wind-affected. Deeper in the snowpack the mid-January surface hoar remains a concern. It can be found down between 40 and 100 cm. In some locations it has reportedly gained quite a bit of strength, but elsewhere it is still producing sudden (popping) failures in snowpack tests. This spatial variability means we'll have to keep an eye on it for a while yet. The mid-December surface hoar layer is now 80 to 140cm below the surface and has become unlikely to fail.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.