Avalanche Forecast

Archived

Mar 5th, 2023–Mar 6th, 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.

Not much improvement in recent days. Wind slabs are still 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 on Saturday. 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

Sheltered areas may have some soft snow on the surface giving decent skiing if you can avoid the tracks. However, at treeline and above expect widespread wind slab conditions that have been producing natural and skier-triggered avalanches over the past few days. Easy shears persist down 25 to 35cm, and 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 is less supportive in areas with only 100cm of snow on the ground. The basal facets/depth hoar persist and continue to give concern for full depth avalanches.

Weather Summary

There is a fair amount of disagreement in weather models for Monday. Some forecasts are calling for mainly sunny conditions, while others predict overcast skies with very light flurries. Everyone seems to agree that the morning will be a chilly -22C with temps rising to -10C or warmer by midday. Winds should be in the moderate range from the south at ridgetop. If any snow does arrive it will only be trace amounts.

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.