Regions
Northwest Coastal.
The storm snow will take several days to settle and stabilize. Make conservative terrain choices and have a safe holiday period.
Confidence
Poor - Due to the number of field observations
Weather Forecast
On Thursday, expect mostly cloudy conditions with light scattered flurries. Freezing levels should be around 800m with light-to-moderate NW wind in the alpine. The next storm system is expected to reach the coast on Friday morning. Friday may see 4-8mm of precipitation with freezing levels around 1000m and light-to-moderate SW wind in the alpine. Saturday may see another 10-20mm with freezing levels around 1000m and light winds.
Avalanche Summary
An early report from Wednesday of natural avalanches up to size 2 from steep terrain features at treeline and the upper part of below-treeline. On Tuesday, natural avalanches up to size 2 were reported from wind loaded areas of the alpine and explosives triggered a few storm slabs up to size 2. Natural activity is expected to drop off quickly but skier triggered slabs will remain a concern for a few days.
Snowpack Summary
Another 20-30cm of snow fell on Tuesday night which makes over 100cm since Friday. This snow sits on the mid-December rain crust which extends up to about 1400m elevation. At higher elevations this snow sits on heavily wind effected surfaces. Strong SW winds have created wind slabs and cornices which may be a lingering concern. The mid and lower snowpack contains some old crust layers but these layers appear to be well bonded.
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.