Avalanche Forecast

Archived

Dec 15th, 2024–Dec 16th, 2024

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

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

Although avalanche activity on the deep persistent layer has tapered over the last few days, it is still possible to trigger this layer (see avalanche table).

Confidence

Moderate

Avalanche Summary

Ski hills reported several small soft wind slabs in immediate alpine lees.
Of note, a group of climbers triggered and got caught in a size two slab that initiated on the deep persistent layer near the ground. This was on the approach to the climb C-Train (above Bow Lake). Climbers self rescued.

Snowpack Summary

5-10 cm recent snow with moderate southerly winds have scoured some alpine areas, and created isolated small wind-slabs in alpine lees. The mid and lower pack is faceted and weak east of the divide, and more settled in western regions. Weak interfaces exist down 20-40 on a facets/suncrust layer, and near the ground on the deep persistent layer (Nov 9 and Oct 20 interfaces). Snowpack depths at tree-line is about 60 cm in eastern areas and 100 cm west of the divide.

Weather Summary

Monday: Mixed sun and cloud forecasted. Valley bottom high temperature of -8 and ridgetop highs of -15. Winds SW in the light range.

Increasing cloud and light flurries along the Divide forecasted for Tuesday

Terrain and Travel Advice

Avoid thin areas like rocky outcrops where you're most likely to trigger avalanches on deep weak layers.
Watch for newly formed and reactive wind slabs as you transition into wind-affected terrain.

Problems

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.