Give all that new snow a bit more time to stabilize before jumping into aggressive terrain. Storm slabs will be especially touchy in areas where high winds have created deep and variable deposits.
Weather Forecast
Tuesday: Cloudy with continuing flurries bringing approximately 5 cm of new snow. Moderate southwest winds. Freezing level to 900 metres with alpine high temperatures of -6.Wednesday: Mainly cloudy with isolated flurries and a trace of new snow. Light west winds. Freezing level to 700 metres with alpine high temperatures of -7.Thursday: Cloudy with isolated flurries and a trace of new snow, increasing overnight. Light west winds, increasing overnight. Freezing level to 600 metres with alpine temperatures of -8.
Avalanche Summary
Reports from Saturday and Sunday showed ski cutting as well as explosives control in the Whistler area producing numerous storm slab results from Size 1-2, as well as several Size 1.5 cornice releases. The most recent storm interface (down about 15 cm at the time) was noted becoming touchy on Sunday afternoon as temperatures rose and winds increased.Throughout this region there has been evidence of a natural avalanche cycle up to size 3 that occurred within the storm snow on Wednesday. More notable are the numerous explosive triggered, very large avalanches up to size 3.5 that where reported near Whistler on Thursday. Two additional explosive triggered 3.5's were reported Friday. These avalanches started in the storm snow and then stepped down to the early January and even the mid-December crusts which resulted in very large avalanches running full path. They occurred on northwesterly aspects below rocky ridgetops between 1950-2200 m.
Snowpack Summary
Another 30-40 cm of new snow from Sunday through Monday brings recent storm totals to around 110-160 cm. This snow continues to be redistributed by extreme southeasterly winds, creating dense storm slabs in lee and cross-loaded features. Impressive cornice growth has also been observed on the lee side of ridgetops. A crust that was buried in early January is buried 230-280cm below the surface at all elevations. Below this there is another crust which was buried in mid-December. Recent explosive control work has triggered storm slab avalanches that have "stepped down" to both of these crusts, resulting in very large avalanches running full path. Although these layers are over 200 cm beneath the snow surface, large triggers such as a falling cornice or a smaller human triggered avalanche do carry a risk of "stepping-down" to these layers. This risk should be diminishing as temperatures cool over the coming days.
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.