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Avalanche Forecast

Archived

Mar 5th, 2020–Mar 6th, 2020

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

Regions

Kananaskis.

Conservative terrain selection is in order. Natural avalanches are occurring.

Confidence

Moderate -

Weather Forecast

Friday will be overcast with steady flurries and strong winds from the SW that will settle down towards the afternoon. Accumulations will be somewhere between 5 and 15cm (weather models disagree). Temperatures should be steady around the -4 mark. Saturday will be another snowy day.

Avalanche Summary

Numerous loose dry avalanches were observed in very steep Alpine terrain on N, NE and E aspects. These were generally small and did not run far down slope. A few naturally triggered slab avalanches were also observed in steep Alpine terrain on SE through N aspects. Average depths of these slides appeared to be between 40 and 60cm and were generally size 2.0 or smaller.

Snowpack Summary

A few more cm's overnight brings recent storm snow totals to 45cm. Unfortunately this storm snow has been significantly redistributed over the last several days by persistently strong to extreme SW/NW winds. Windward slopes are stripped to bare rock, and lee and cross-loaded terrain is heavily wind loaded. Expect to find wind slabs in virtually all Alpine and Treeline terrain where there is still snow on the ground. These wind slabs will be of widely variable depths and densities, and will be ripe for human triggering in much of the region. On the positive side, this season's midpack is generally strong and well consolidated. In shallow snowpack areas, the basal weaknesses remain, and will be on our radar for the remainder of the season.

Terrain and Travel

  • Avoid freshly wind loaded terrain features.
  • Avoid lee and cross-loaded terrain.
  • Extra caution is needed around cornices under the current conditions.
  • Make conservative terrain choices and avoid overhead hazard.
  • Be aware of the potential for large avalanches due to the presence of a deep persistent slab.

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.