Avalanche Forecast

Archived

Dec 30th, 2025–Dec 31st, 2025

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

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.

Great skiing continues during a break in snowfall. Watch for reactive wind slabs in exposed alpine and treeline terrain, and be mindful of deep persistent weak layer when transitioning into areas with a thinner snowpack.

Confidence

High

Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.

Avalanche Summary

No new natural avalanche observations were reported on Tuesday.

In the past couple of days, local ski hills triggered several size 2 wind slabs in the alpine using explosives and one 2.5 deep persistent slab in a thin rocky area.

On Sunday, a skier-remote size 2 deep persistent slab was reported in the Lake Louise backcountry (see photo below). Although avalanche activity on the deep persistent layer has slowed, we continue to receive sporadic evidence of its reactivity.

Snowpack Summary

Variable NW-SW winds have created fresh windslabs in alpine and open treeline terrain. In sheltered areas, recent storm snow (20-30 cm) remains preserved.

There is 40-80 cm over the Dec 15 melt-freeze crust (which is present to 1800-2000 m), 80-160 cm over the November facet/crust interfaces, and, in thinner snowpack areas, facets at the base.

Treeline snow depths range from 100-200+ cm.

Weather Summary

Expect a mix of sun and clouds on Wednesday, with moderate to strong W/SW ridgetop winds. Tree line temperatures will remain steady near -5°C, and no new precipitation is expected.

Over the next few days, temperatures will remain fairly stable with freezing levels near the valley bottom, and winds will become light from the W/SW, with no significant snow.

Link to the weather forecast

Terrain and Travel Advice

Watch for newly formed and reactive wind slabs as you transition into wind-affected terrain.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Avoid thin areas like rocky outcrops where you're most likely to trigger avalanches on deep weak layers.

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.