The recent storm has loaded 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.
Weather Forecast
Tonight and Monday: Isolated flurries / Winds moderate to strong westerly / Freezing rising through the day up to 2000mTuesday: Cloudy / Winds moderate to strong westerly / Freezing continue to rise as high as 2500m.Wednesday: Clearing with sunny periods / Winds moderate to strong westerly / Freezing level 2500m.
Avalanche Summary
Most people were wisely avoiding the back country yesterday so we have not received a lot of observations from the Sea to Sky. Operations in neighboring regions reported a widespread natural avalanche cycle with numerous large to very avalanches. Some reports indicate isolated avalanches that are failing down on an old facet layer just above the ground.
Snowpack Summary
Saturday's storm clobbered the region with up to 100 cm of snow accompanied by strong winds (Whistler Blackcomb recorded gusts at ridge top up to 170km/h). The unrelenting southwest to south winds have formed large and touchy wind slabs in the alpine and at treeline. A widespread avalanche cycle has likely cleared out much of the surface hoar from early in January.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.In glaciated terrain open and poorly bridged crevasses are everywhere although now they are hiding under a meter of unsupportive storm snow.
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.