Confidence
Fair - Forecast snowfall amounts are uncertain on Friday
Weather Forecast
Thursday night: 10-15cm snow. Freezing level 900m.Friday: 5-10cm snow. Freezing level rising briefly to around 1300m near the coast, then falling back to 900m. Strong westerly winds.Saturday: A cool sunny day. Sunday: Dry but mild, with cloudy periods possible.
Avalanche Summary
Numerous Size 1-3 slab avalanches (both natural and human triggered) have been reported in the past 72 hours. Skiers accidentally triggered avalanches in Garibaldi Park (Wednesday) and in the backcountry near Blackcomb (Thursday). In both cases they had a lucky escape. I expect to see continued avalanche activity; however we are getting into a period where there will not be as many obvious clues of danger: natural avalanching will decrease but human-triggering will probably increase.
Snowpack Summary
Around 20cm snow fell last night bringing the total snowfall in the past week to 100-170cm. Wind slabs have formed in exposed NW-E facing slopes, probably as deep as 100cm in some areas. Cornices have grown large and could act as a trigger for large avalanches. A weak rain crust is found below the new snow up to treeline elevations. This crust may sit on top of buried surface hoar and/or facets. One observer near Whistler reported whumpfing on a buried surface hoar layer in low-angle terrain below treeline. Watch this layer as it gets more load and a thick cohesive slab develops, particularly below treeline where the buried surface hoar would be especially large. A strong mid pack overlies basal facets that have also gained considerable strength. On average the snowpack is around 200cm deep near treeline.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
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.