Regions
Northwest Coastal.
Avalanche danger is increasing with the on-going storm. Expect danger to be HIGH by Thursday or earlier if you get more snow than forecast in your area.
Confidence
Poor - Due to the number and quality of field observations
Weather Forecast
Moderate precipitation is expected to continue overnight. Coastal ranges in the west of the region may see 20-40 mm of water equivalent in the 24 hours preceding Wednesday morning. The areas that see the most precipitation are also expected to have the warmest temperatures; coastal freezing levels may reach 1500 metres. Expect a bit of a lull between low pressures systems on Wednesday, with the next system hitting the north coast on Wednesday night. Thursday should be wet and windy as the storm pushes into the region from the south. Friday should bring another gap between systems.
Avalanche Summary
No new avalanches reported. I suspect that new storm slabs are developing and may be easily triggered by light additional loads.
Snowpack Summary
The snowpack is highly variable across different aspects and elevations. So far, we only have limited information from the field. Initial reports suggest that there is around 150 cm at 2000 m. Recent winds have scoured exposed slopes, and left variable wind slabs and crusts. In some places, a crust/facet interface or surface hoar can be found in the upper snowpack. At high elevations, a crust which formed early season may exist near the base of the snowpack. The new storm snow may not bond well to the mix of old surfaces left behind after the recent high pressure. Buried surface hoar may be found below the new storm snow at lower elevations, or in areas where the recent temperature inversion was not strong enough to melt it.
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.