Winter hasn't fully loosened its grip at higher elevations. Conditions remain dynamic as yet another storm rolls through the region.
Weather Forecast
Saturday night: Flurries bringing up to 10 cm of new snow. Moderate to strong southwest winds.Sunday: Cloudy with continuing flurries bringing a trace to 5 cm of new snow . Light south winds. Freezing level to 1600 metres with alpine temperatures of -3.Monday: A mix of sun and cloud with isolated flurries and a trace of new snow. Light east winds. Freezing level to 1800 metres with alpine temperatures of -2.Tuesday: Cloudy with flurries bringing approximately 5 cm of new snow. Light to moderate south winds. Freezing level to 1700 metres with alpine temperatures of -3.
Avalanche Summary
Reports from Friday showed significant cornice activity in the Whistler area, with several natural Size 2 releases and one Size 3.5 that triggered a large slab avalanche with a roughly 2 metre deep crown fracture. One of the Size 2 releases also triggered a 100 cm deep slab. Other natural and explosives triggered cornices ranged from Size 2-3 and mainly entrained loose snow, but a few thinner slabs were also triggered.Reports from Thursday included observations of several explosives controlled cornice releases in the Whistler area. Sizes ranged from 1.5 to 2.5 and one release successfully triggered a 15-30 cm by 15 m slab below it. Wednesday's reports showed explosives triggered storm slabs reaching Size 1.5 in the Whistler area. Crown depths averaged 20 cm.
Snowpack Summary
Light snowfall will combine with moderate to strong southerly winds to form fresh wind slabs on the surface at higher elevations over Saturday night. Below the new snow, warm temperatures and sunshine recently moistened surface snow on most aspects and elevations. New snow will form a variable bond with this surface, with a weaker bond expected at higher elevations and northerly aspects where a crust may have formed in advance of new snow accumulations. The mid and lower snowpack are generally well settled and strong, however large cornice releases have recently demonstrated a capacity for triggering large slab avalanches on underlying slopes.
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.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.