Avalanche Forecast

Archived

Feb 26th, 2023–Feb 27th, 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.

Regions

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

Conservative terrain choice is the best approach. The snowpack needs more time to heal. Avoid wind loaded areas in the alpine and at tree line.

Confidence

Moderate

Avalanche Summary

On Saturday, the forecast team witnessed some natural avalanche activity near Tent ridge in the size 2-2.5 range. On Sunday, more evidence of a wider cycle near Mt. Murray area was observed and appeared to be 24-36 hrs old. Some more natural activity could be expected and ski triggering is still likely.

Snowpack Summary

The wind continued to blow on Sunday moving the snow around. Presently, there are widespread wind slabs everywhere and on all aspects in the alpine, at tree line and open areas in the trees. This is due to last week's storm that left us with 30-50cm of snow with strong winds from all directions. The avalanche activity from these wind slabs might have slowed downed but still cannot be trusted because they are either sitting on an older pencil wind crust or on top of facets depending where you are. The alpine is still variable in terms of depth of snow. The November facets make up the bottom 50-70cm of the snowpack and there is anywhere from 40-110cm sitting on top of it. Our biggest concern is triggering the wind slab which then has a high potential to produce large avalanches bringing the whole snowpack with it. Good skiing can still be found in low avalanche hazard areas that are either in the trees or were sheltered from the wind. Travel in the forest is still challenging as you are at times still punching through the facets to ground.

Weather Summary

2-4cm of snow is expected Sunday night. Monday will be a mix of sun and cloud with flurries starting in the late evening. Temperatures will be between -20c and -12c. Winds on Monday are expected to be 25-30km/hr form the SW.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
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.