Cold temps have helped to stabilize the snowpack, but sunshine and above freezing temps in the alpine are forecast. Expect the snowpack to be touchier if temps are warming up. The Winter Permit System is now in effect.
Weather Forecast
A high pressure system will keep the region dry and clear, with light northerly winds through the weekend. Expect cold temps in the valley bottoms, but a temperature inversion is expected to develop with above freezing alpine temps. Valley cloud will likely accompany the inversion.
Snowpack Summary
Strong northerly winds yesterday reverse loaded southerly aspects creating wind slabs. These slabs overlie a variety of surfaces, including suncrust on steep S-SW aspects, with 2-3mm surface hoar on most other aspects. Below this, the snowpack as a whole is strengthening. A weak basal layer exists on alpine N/NE aspects.
Avalanche Summary
Avalanche control yesterday triggered a few slabs to size 2.5. Reverse loading by strong Northerly winds triggered one size 2 slab avalanche as well. A skier-triggered size 2 from a SW aspect, at ~2200m, was reported in the McGill area on Tuesday: 30cm deep, 40m across, running 200m in length.
Confidence
Timing or intensity of solar radiation is uncertain
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.