Regions
Northwest Coastal.
Heavy snowfall and strong winds will push the Avalanche Danger to High.
Confidence
Fair - Intensity of incoming weather systems is uncertain on Monday
Weather Forecast
Expect lingering snowfall (up to 15cm) on Monday morning as Sunday's storm tapers-off. A clearing trend is forecast for late Monday and Tuesday. By Wednesday, a strong Pacific low will deliver another round of moderate to heavy snowfall. Ridgetop winds will remain moderate to strong from the southwest on Monday, decreasing somewhat on Tuesday, and then becoming strong and southwesterly with Wednesday's storm. Freezing levels should hover around 600m for the forecast period.
Avalanche Summary
There was surprisingly little reported avalanche activity given the amount of new snow and wind on Thursday and Friday. Size 1 soft slabs were reportedly sensitive to human triggering in high elevation lee terrain. Looking forward, more wind and snow on Sunday and Monday will likely spark a round of natural storm slab activity. New new snow will also add more stress to these recently buried weaknesses.
Snowpack Summary
Just before the weekend, between 10 and 40cm of new snow fell with the highest accumulations occurring in the southwest of the region. The new snow and strong southwest winds built dense slabs on exposed lee features. Locally heavy snowfall and strong winds on Sunday and Monday morning will add size and destructive potential to this developing storm slab. Below the recent storm snow you'll find a variety of interfaces including old hard wind slabs, hard crusts, surface hoar, and/or surface facets. Some reports suggest a reasonable bond at this interface, although I'd remain cautious on steeper, high-consequence slopes as a release on recently buried surfaces could be large and destructive .At the base of the snowpack, weak facets may be found, particularly on alpine slopes in the north of the region. Cornices are reported to be large and potentially unstable.
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.