The recent storm is loading an unusually thin snowpack above a week layer near the ground. The "wait 48 hours and you're good" Coastal mantra does not apply right now as these conditions are likely to persist for some
Confidence
Fair - Intensity of incoming weather systems is uncertain
Weather Forecast
Tonight and Sunday: Snow tapering off tonight, scattered flurries Sunday / Winds moderate to strong westerly / Freezing level 800mMonday: Isolated flurries / Winds moderate to strong westerly / Freezing rising through the day up to 2000mTuesday: Cloudy / Winds moderate to strong southwesterly / Freezing continue to ri8se as high as 2500m.
Avalanche Summary
Natural avalanche activity was report to have intensified Friday although these avalanche were a result of developing to storm slabs. Earlier in the week a deep slab avalanche was triggered by a snow cat at Whistler Blackcomb. This avalanche highlights the potential for large and deep avalanches in many areas on the South Coast. As heavy loading continues through the day expect more large deep avalanches.
Snowpack Summary
Saturday's storm clobbered the region with another 60-80 cm of snow accompanied by strong winds (Whistler Blackcomb recorded gusts at ridge top up to 170km/h). A total of 60-80 cm of new snow has fallen in the last few days and may overlie surface hoar in sheltered terrain. The unrelenting southwest winds have formed large and touchy wind slabs in the alpine and at treeline.The cold temperatures of early December left persistent weak faceted crystals that seem to be variably reactive. At higher elevations where the snowpack was deeper, the facets likely co-exist with a crust in the mid pack. At lower elevations or in shallow, rocky areas of the alpine, the facets are most likely more widespread and may exist down near the ground. Either way, the "wait 48 hours and you're good" Coastal mantra does not apply as these conditions are likely to persist for some time.Early season riding hazards such as rocks, stumps and logs are lurking below the surface in many areas, especially at lower elevations. In glaciated terrain open and poorly bridged crevasses are everywhere.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.