Avalanche Forecast

Archived

Mar 4th, 2023–Mar 5th, 2023

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 avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Kananaskis, Bow Valley, Highwood Pass, North 40, Spray - KLakes.

Wind slabs are sensitive to human triggering and some natural activity has been occurring. We sound like a broken record, but this is a year to stick to low-angle slopes and limit exposure to overhead terrain.

Confidence

Moderate

Avalanche Summary

One size 2 naturally triggered slab avalanche was observed on Mt Rundle in a steep alpine bowl on a NE aspect. This avalanche appeared to fail in the deep persistent weak layer of basal facets. On Friday a size 2 avalanche was observed in the Buller Mountain area that was triggered by a cornice collapse.

Snowpack Summary

Up to 35cm of recent storm snow has been blown into wind slabs at treeline and above. Sheltered areas may have some soft snow on the surface giving decent skiing. Easy shears persist down 25 to 35cm and have have seen some reactivity to skier traffic. Moderate shears have also been found down 30 to 50cm on various versions of old wind slab interfaces. The midpack is strong in deeper snowpack regions near the divide, but the basal facets/depth hoar persist. An avalanche initiated in the upper snowpack could easily step down to the deep persistent weak layers, causing a very large avalanche. This season it is important to always have full depth avalanches on your mind.

Weather Summary

Very light flurries through Saturday will likely only amount to 2cm by Sunday morning. Temperatures will range between -20 and -13 with clearing skies later in the day. Winds will be moderate from the SE.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.