Avalanche Forecast

Archived

Nov 29th, 2021–Nov 30th, 2021

Alpine

Natural avalanches possible, human triggered probable.

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.

While natural avalanche activity has tapered a bit, wind slab conditions are prime for human triggering at upper elevations. Avoid avalanche terrain. We are at the upper level of "Considerable" hazard.

Confidence

Moderate -

Weather Forecast

Tuesday will be a mix of sun and cloud with light flurries. Accumulations are likely to be less than 5cm. Freezing levels should hold steady at about 1700m with daytime highs near -4 in the Spray Valley. Winds will be in the moderate to strong range from the SW. Another storm is expected Wednesday with up to 25cm and 150km/h winds!

Avalanche Summary

A few naturally triggered slab avalanches up to size 2 were observed today, mainly in Alpine terrain. This adds to the numerous avalanches observed yesterday up to size 3 that had run well into their historic paths.

Snowpack Summary

24 hour snowfall amounts are difficult to quantify as the recent storm came as rain and snow. At Highwood Pass today ski pen was 30 to 40cm in thick cakey snow. Winds have remained strong for many days, which has contributed to widespread wind slab development in the Alpine and open areas at Treeline. These fresh slabs seem prime for human triggering. At lower elevations, below approximately 2000m, there is a skiff of snow over a freshly formed rain crust.

Terrain and Travel

Avoid freshly wind loaded terrain features.
Approach lee and cross-loaded slopes with caution.
Avoid areas with a thin or variable snowpack.
Ice climbers should be equipped with avalanche safety gear.

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.