Expect a big difference in precipitation amounts and temperatures from Howe Sound (warm and wet) up to Whistler (not quite as warm or wet). Regional conditions could vary quite a bit this weekend.
Confidence
Fair - Due to the number of field observations
Weather Forecast
Friday: Cloudy with showers or flurries (trace to 5mm). The freezing level is 1800-2000 m. Ridge winds are 30 gusting to 50 km/h from the south. Saturday: Periods of rain of snow (10-20 mm). The freezing level should drop from 2100 to 1600 m. Winds ease to light from the southwest. Sunday: Probably a drier day. Freezing levels should jump up to 2000-2200 m. Winds are moderate from the south.
Avalanche Summary
There was one report of an avalanche that released from a rocky sun-exposed slope near Whistler on Tuesday, but details on this slide are limited. No other avalanches have been reported.
Snowpack Summary
The current snow surface is highly variable with surface hoar or facetted snow reported in sheltered areas, and pockets of wind slab or a crust (from last weeks rain) in open wind-exposed terrain. Recent cold temperatures have created a strong temperature gradient in the upper snowpack resulting in facetting of the most recent snow. Winds during the past week have been variable and have blown snow into dense wind slabs on a variety of aspects or has cross-loaded gulley features. A solid rain crust is buried 10-20 cm deep at and below treeline. Another crust that was buried in mid-November is down 40-60 cm. The snow pack depth drops significantly below treeline with essentially no snow below 1600 m.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.