Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Dec 20th, 2024–Dec 21st, 2024

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.

The recent new snow and strong winds have resulted in an elevated avalanche danger that remains in the forecast region.

Confidence

Moderate

Avalanche Summary

The ski hills continue to report triggering of wind slabs with ski cuts and explosives, ranging up to size 2, and 10 to 40 cm deep.

There is visible evidence of a widespread avalanche cycle that occurred during the storm, particularly in the western parts of the region. We have observed failures at both the wind slab interface and the deep persistent problem.

Snowpack Summary

Up to 20 cm of storm snow fell last week. This new snow, combined with strong winds, has formed wind slabs throughout the alpine and treeline. The mid and lower pack is faceted and weak east of the divide, and more settled in western regions. A weak interface exist 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

A series of weak systems will move through the forecast region over the weekend. Light precipitation could result in 2 to 5 cm of snow accumulation by Monday. Winds at higher elevations will remain elevated, and temperatures at valley bottoms will hover around 0°C.

Terrain and Travel Advice

  • Avoid freshly wind-loaded features, especially near ridge crests, rollovers, and in steep terrain.
  • 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.