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Avalanche Forecast

Archived

Feb 21st, 2013–Feb 22nd, 2013

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
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.

Regions

Little Yoho.

If the weather forecast comes to fruition on Friday, expect an increase in hazard through the weekend.

Weather Forecast

A fast moving low pressure system is forecast to give us 15-20cm and strong Westerly alpine winds starting sometime in the afternoon on Friday.  Timing and intensity of this one is hard to predict, but expect worsening weather in the afternoon. The highest amounts are forecast for North and West of Lake Louise (Wapta region)

Snowpack Summary

Thin snowpack areas at all elevations are  weak and facetted, as well as most below treeline areas up to around 1900 meters.  Previous storm snow has settled to approximately 10cm.  This snow sit on top of wind slabs, both soft and hard, in alpine lee areas.

Avalanche Summary

No activity reported today.  Avalanche control on Wednesday produced avalanches up to size 3.  Cornices that were triggered provided enough of a rake to entrain all of the facets in the path, running to within 100m of the road on Mt. Whymper (Kootenay) and Mt. Dennis (Yoho). 

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Friday

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.