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Avalanche Forecast

Archived

Apr 11th, 2013–Apr 12th, 2013

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

Regions

Little Yoho.

It will feel wintery the next few days, with continued storms piling into us from the west. Danger ratings will increase during the peaks of each storm wave.

Weather Forecast

Clear skies should greet us tomorrow morning. Then another storm is lined up to pass through the forecast region Friday evening, delivering 10-15cm of snow with moderate westerly winds and freezing levels below 1300m.

Snowpack Summary

We received 10-15cm overnight, accompanied by moderate to strong SW winds. This will have developed into soft slabs in the alpine. Expect the slabs to be touchy for the next day or two. These slabs overlay 10-30cm of previous storm snow, which rest on suncrusts on solar aspects and facetted snow on polar aspects.

Avalanche Summary

Touchy soft slabs in the Lake Louise area and up highway 93N were reported in the immediate lees of ridgecrests. Slabs were on average 10-15cm thick, but in some cases up to 30cm thick.

Confidence

Forecast snowfall amounts are uncertain

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.

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.