Avalanche Forecast

Archived

Jan 29th, 2012–Jan 30th, 2012

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Sea To Sky.

Confidence

Fair - Intensity of incoming weather is uncertain on Tuesday

Weather Forecast

Monday: very light snowfall / moderate southwest winds / freezing level at 700m Tuesday: light snowfall becoming moderate overnight / light to moderate southwest winds / freezing level at 900m Wednesday: light snowfall in the morning with a clearing trend developing in the afternoon / light to moderate west winds with rising freezing levels

Avalanche Summary

Numerous size 1 windslab avalanches were reported from the Whistler area in response to windloading on Sunday. Observations were limited due to poor visibility.

Snowpack Summary

The region saw variable amounts of snow with moderate winds and warmer temperatures on Sunday. The result is fresh, cohesive windslabs on lee features at treeline and in the alpine. These new windslabs are resting on impressive amount of storm snow that fell last week. By now I suspect that last week's storm snow has gained considerable strength.About a metre down there are a variety of older snow surfaces. These surfaces include lower density snow which may have had seen some faceting, old wind slabs, and crusts. These interfaces have most likely gained considerable strength, but triggering may be possible with a heavy load in isolated terrain. Previous concerns about deeper persistent weak layers appear to have diminished.Snowpack depths at treeline are in the region of 260 cm.

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.

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.