Regions
Northwest Coastal.
Avalanche danger is expected to decrease as things dry out and cool off.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
The stormy pattern is expected to continue on Wednesday before a drying trend later in the forecast period. Wednesday: Expect another 10-15cm with freezing levels dropping to 800m and moderate southwesterly ridgetop wind. Thursday: 5-10cm of snow with freezing levels dropping to valley bottoms and moderate southeasterly ridgetop wind. Friday: Mainly cloudy with light flurries possible. Freezing level around 500m and light westerly ridgetop wind.
Avalanche Summary
Recent reports of natural, rider and remotely triggered large slab avalanches from the mountains around Shames suggest that the load on a layer of recently buried surface hoar has reached critical levels.
Snowpack Summary
Sustained snowfall continues to load the old snow surface from late November, which may be getting down close to a metre at treeline elevations. These fresh storm and wind slabs are bonding poorly to a variety of weaknesses including crusts, facets and buried surface hoar. The most critical of these is the buried surface hoar, which has the potential for remote triggering, wide propagations and prolonged sensitivity to triggers. It is likely lurking in most sheltered areas treeline and below and has been spotted well into the alpine in Bear Pass. Deeper in the snowpack, weak crusts and facets near the ground maintain the possibility of step-down deep slab triggering.
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.