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Avalanche Forecast

Archived

Dec 30th, 2012–Dec 31st, 2012

Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Little Yoho.

Stability is generally good; however, the cold temps are taking their toll in thin snowpack areas. Watch for loose dry avalanches in areas that are completely facetted along with cornice failures on alpine slopes.

Weather Forecast

A blocking ridge of high pressure will bring sunny skies, cold nights and light northerly winds through the forecast period. Conditions are prime for daytime inversions which means it will be warmer in the alpine than in the valley bottom, although alpine temperatures shouldn't approach zero degrees celsius.

Snowpack Summary

20-40cm thick wind slabs exist in high alpine features and are stubborn to unreactive from field reports.  W of the divide, a well settled snowpack exists in deeper locations with the basal Nov 6 crust well bonded.  In the front ranges E of the divide, a mainly facetted snowpack exists with the Nov 6 basal crust being mainly facetted. 

Avalanche Summary

Lake Louise ski area reported a small, skier triggered avalanche in a steep, thin treeline area today.  This was a loose dry avalanche in an area with a completely facetted snowpack. In a deeper snowpack area, a large cornice failure was reported above the Bourgeau LH ice climb, but did not trigger a slab.

Confidence

The weather pattern is stable

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

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.