A buried weak layer means tricky conditions will persist for several days. Make conservative terrain choices and have a safe holiday period.
Confidence
Poor - Due to the number of field observations
Weather Forecast
A ridge of high pressure should keep the region dry for Thursday and Friday. On Thursday, expect mostly sunny conditions with freezing levels around 700m and light NW winds in the alpine. Friday is expected to start out sunny with increasing cloudiness during the day. Freezing levels should be around 500m and alpine winds should remain light. The next weak storm system is currently expected to arrive Friday night and persist through the weekend. Saturday may see 4-8mm of precipitation with freezing levels staying relatively low.
Avalanche Summary
On Tuesday, several natural size 1 wind slabs were reported. On Monday, reported avalanche activity was limited to one natural cornice release that did not trigger a slab as well as loose sluffing from steep terrain. On Sunday, explosive control produced storm slabs size 1-2. Going forward, natural activity is not expected but skier triggered slabs may persist for several days.
Snowpack Summary
A 40-60 cm storm slab sits above the mid-December surface hoar layer. We don't know a whole lot about the reactivity of the layer yet but appears to be most reactive at treeline in the north of the region. It may be less reactive in the Whistler area. Winds prior to burial likely destroyed the surface hoar in the alpine throughout most of the region. Strong SW winds during the storms created wind slabs which may still be a concern.
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.