Storm slabs continue to develop with each load of new snow. Deep pockets of wind transported snow may exist at higher elevations.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Another pulse of Pacific moisture should bring 10-20 cm to treeline elevations by Monday morning combined with moderate southwest winds and freezing levels around 500 metres. Convective flurries during the day Monday with periods of broken skies. Another 5-8 cm by Tuesday morning with light winds. Another pulse of cool moist air moving across the region on Wednesday should bring 10-20 cm.
Avalanche Summary
Soft new storm slabs releasing up to size 2.0 and new cornices releasing naturally to size 1.5 at Whistler.
Snowpack Summary
Another 30 cm of new snow on Sunday morning, continues to add to the developing storm slabs. Cool temperatures down to around 400 metres has resulted in dry snow at all but the lower BTL elevations. Strong winds overnight in the alpine created deep pockets of wind transported snow that were reported to be easy to trigger. There may be a slight change in the hardness of the snow down about 60-80 cm due to temperature changes of individual snowfalls. This may be the most likely depth for shears in snowpack tests. The December 8th crust is down about 120 cm and has been reported to be well bonded. The storm snow is the biggest problem at this time. It may be difficult to forecast when the incremental storm amounts combine to create enough loading over a weakness to result in large avalanches.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.