Another punchy storm will result in high avalanche danger in the Sea to Sky region on Thursday. Use caution heading into the backcountry at this time.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
WEDNESDAY NIGHT: 20-30 cm new snow is expected overnight.THURSDAY: 20-30 cm new snow with freezing levels rising to around 1400 m. Strong southwesterly winds.FRIDAY: 10-15 cm new snow. Freezing levels rising to around 1800 m. Strong southerly winds.SATURDAY: 2-4 cm new snow, brief periods of clear weather. Freezing levels around 800 m. Light southwesterly winds.
Avalanche Summary
Several natural avalanches were reported from Wednesday in the recent storm snow at around 2000 m. The typical size of the releases so far appears to be size 2. However, I expect the typical size to increase as there is significant amounts of new snow in the forecast.
Snowpack Summary
Snowfall beginning Sunday has deposited up to 80 cm in the Sea to Sky region. Strong to extreme southwesterly winds have accompanied the new snow and the weather forecast is calling for additional snowfall amounts to accumulate 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 not bonding well with the old surface layer, has slab-like properties, and is reacting to skier traffic.Prior to this storm, alpine snowpack depths varied around 150-200 cm, with an early November crust at bottom of the snowpack (down 100-120 cm). 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 1800 m).
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.