Regions
Northwest Coastal.
Continued stormy weather will maintain elevated avalanche danger this week.
Weather Forecast
Synopsis: We could see a short lull in the weather on Thursday before another strong frontal system hits the North Coast on Friday. Expect 10-20 cm (mm) tonight and Thursday followed by 30-45 cm (mm) on Friday. The freezing level should be between 1400-1800 m and winds are strong from the southwest. Saturday looks like another lull in intensity but we could still see 15-20 cm with a freezing level a couple hundred metres lower.
Avalanche Summary
Heavy snow or rain, and strong upper winds are probably producing a widespread natural avalanche cycle throughout the region. Expect wet activity below treeline and the potential for large storm slabs and isolated deep slabs from higher terrain. This pattern should continue for most of the week.
Snowpack Summary
Heavy snowfall (with rain below 1000 m) and strong southwest winds will build deep and dense storm/wind slabs throughout the week. The slab will likely be 'upside down' with warming temperatures dropping moist or dense snow on previous dry lower-density snow. A buried rain crust and/or surface hoar layer is down about 60-80 cm. Observations of the strength at this interface have been limited. The November crust near the bottom of the snowpack is generally well bonded, but may 'wake up' with intense loading this week. There is potential for isolated very large and deep avalanches.
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.
Wet Slabs
Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.