Significant snowfall accumulation will drive up avalanche hazard.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
MONDAY NIGHT: Flurries, accumulating up to 20 cm overnight, moderate gusting strong south wind, freezing level below 1000m. TUESDAY: Snow, accumulation 15-30 cm, moderate southwest wind with strong gusts, freezing level rising to 1400m. WEDNESDAY: Continued snow, accumulating 20-35 cm, moderate southwest wind with strong to extreme gusts, freezing level below 1000m. THURSDAY: Snow, accumulating up to 30cm, moderate southwest wind with extreme gusts, freezing level 1200m.
Avalanche Summary
The new storm snow is bonding poorly to the old surface, small (size 1) storm slabs are reacting to skier traffic around Whistler and larger avalanches (up to size 2) have been triggered by explosives. Expect avalanche activity to increase with more snow on the way along with wind.
Snowpack Summary
Snowfall beginning Sunday has added up to 30cm around the region. The weather forecast is calling for significant snowfall amounts through the week. Buried under the new snow is a weak surface layer sitting over 20-30 cm of low density faceted snow. The new snow is initially not bonding well with this old surface layer.Prior to this storm, alpine snowpack depths varied around 150-200 cm, with an early November crust at bottom of the snowpack (down 100-120cm). This crust appears to be breaking down at higher elevations and has been unreactive to snowpack tests. Snowpack depths disappear quickly with decreasing elevations (starting around 1800m).
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.