Avalanche Forecast

Archived

Mar 3rd, 2020–Mar 4th, 2020

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 possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Kananaskis.

More snow and wind are on the way. Avalanche hazard is trending up.

Confidence

Moderate -

Weather Forecast

10 to 15cm of new snow is expected by Wednesday morning along with strong to extreme SW winds. Temperatures will range from -5 to -10 in the Alpine. Thursday looks like a mostly sunny day before another snow storm arrives Friday.

Avalanche Summary

Very limited observations today, but one large avalanche was noted off an eastern aspect of Grotto Mountain today around 2pm. The slide was difficult to see, but the powder cloud extended from ridgetop to valley bottom, so it is estimated that this was a size 2 to 2.5 wind slab avalanche initiated by wind loading.

Snowpack Summary

Up to 5cm in the past 24 hours adds to the recent storm snow totals of nearly 30cm. This recent snow has been redistributed by persistent strong to extreme SW winds. Expect wind slabs in virtually all terrain features except the most sheltered of areas. These wind slabs are reactive to skier triggering in steeper terrain. Cornices are also quite large, and more failures have occurred in recent days. Otherwise the mid pack remains dense and strong in traditionally thicker snowpack areas (generally further west closer to the divide). The basal facets remain a concern in the back of our mind as they appear to be with us for the entire season.

Terrain and Travel

Avoid freshly wind loaded terrain features.
Avoid lee and cross-loaded terrain.
Avoid exposure to slopes that have cornices overhead.
Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.

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.

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.

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.