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Avalanche Forecast

Archived

Mar 28th, 2017–Mar 29th, 2017

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

Regions

Kananaskis.

Natural avalanche activity is subsiding and hazard ratings are slowly dropping, but it is still possible to have full path avalanches. An Avalanche Canada BLOG explores this issue.

Confidence

Moderate - Freezing levels are uncertain

Weather Forecast

Wednesday will be mainly cloudy with isolated flurries and Alpine temperatures near -5 °C. Winds will be moderate from the SW, and the freezing level will climb to 2000 metres. Thursday looks to be a mostly sunny day with light winds and high freezing levels.

Avalanche Summary

One naturally triggered size 1.0 wind slab was observed on a NE aspect at 2300m. This slab was only 15cm thick and did not run far. Also, a size 1.5 cornice failure was observed on a N aspect at 2700m. This cornice failed at approximately 14:00hrs and did not propagate a slab on the underlying slopes.

Snowpack Summary

Up to 5cm of new snow in the past 24hrs. In sheltered areas there is now 25cm of low density snow overlying previous surfaces. On solar aspects there are now various buried crusts. Strong winds today led to further wind slab development in the Alpine and isolated areas at Treeline. Easy shears were observed down 10 and 25cm. The snow was moist this afternoon below 1900m. The middle of the snowpack is generally well settled and dense, while the base of the snowpack consists of over 100cm of depth hoar and facets. Natural avalanche activity has tapered off, but the structure of the snowpack continues to cause concern to forecasters for "low probability, high consequence" avalanches.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

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.