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 17th, 2024–Dec 18th, 2024

Alpine
Natural avalanches possible, human triggered probable.
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.
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.

Lots of uncertainy about how much snow will fall with this storm, but with strong winds and new snow the avalanche hazard will rise on Wednesday.

If snowfall amounts are higher than forecast the danger may increase to HIGH in some areas. Monitor snowfall amounts closely and choose more conservative terrain if needed.

Confidence

Moderate

Avalanche Summary

We expect an increase in avalanche activity on Wednesday with new snow and strong west winds.

On Sunday, we received two separate reports (Report 1/Report 2) of large, human-triggered avalanches in the Highway 93N backcountry. Both avalanches involved a stiffer slab failing on the deep persistent facets/depth hoar on N/NE aspects. Recent natural avalanche activity on this layer has been minimal, but it remains active and continues to be the primary avalanche concern.

Snowpack Summary

Increasing west winds and new snow will create wind slabs in lee areas at treeline and in the alpine. This new snow will sit over a weak faceted midpack, with very weak basal facets/crusts near the ground. Western areas of the forecast region have similar layers but a slightly deeper, denser snowpack with fewer facets. Snowpack depths at tree-line are 40-60 cm in eastern areas and 100 cm west of the divide.

Weather Summary

Tuesday night: Snow begining in the evening with 5 cm expected overnight accompanied by strong west winds.

Wednesday: Snow continuing with an additional 5-10 cm expected throughout the day. Strong west winds continue through the day. Treeline temperatures remain steady near -7°C.

Note: Local snowfall amounts may be higher than expected with this storm.

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.