Avalanche Forecast

Archived

Jan 30th, 2017–Jan 31st, 2017

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Kananaskis.

Another wave of cold weather on Tuesday and Wednesday will do nothing to improve the basal facets. Caution is advised in steep terrain as dense wind slabs overlie these weak base layers.

Confidence

High -

Weather Forecast

Tuesday will be a mix of sun and cloud with a high of only -18 °C. Winds will be light from the North, but will feel brisk! The cold weather hangs around for a couple of days. There is no precipitation expected in the near future.

Avalanche Summary

A Mountain Information Network (MIN) report was submitted yesterday sharing a close call by a party ski-touring in the Hero's Knob area. The remotely triggered a size 2.0 slab avalanche from 100m away. This occurred at approximately 2300m on a SE aspect. The slab was reported as 80cm thick, so it is quite possible that the failure plane was the Dec 18th persistent weak layer. See the MIN posting for more information by zooming in on the blue flag in the Hero's Knob area.

Snowpack Summary

Wind slabs are widespread in lee and cross-loaded features in the Alpine and in open areas at Treeline due to recent extreme westerly winds. These slabs sit on a weak and faceted mid-pack and basal layers. The snowpack at lower elevations remains shallow, weak and facetted and only supports the weight of a skier on previously established paths.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.

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.