Avalanche Forecast

Archived

Dec 6th, 2023–Dec 7th, 2023

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.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

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

An avalanche cycle is continuing with up to 45 cm of heavy wet storm snow overlaying a generally weak and faceted lower snowpack. Conservative terrain choices without overhead hazards are recommended for skiers and climbers.

Confidence

No Rating

Avalanche Summary

Numerous natural, skier and explosive triggered avalanches up to size 2.5 were reported on Wednesday, including remotely triggered avalanches during ski cutting. These were failing as storm slabs and deep persistent slabs at all elevations. Widespread whumphing and cracking was reported in areas not steep enough to avalanche.

Snowpack Summary

Up to 45 cm of dense storm snow overlays a weak Dec 2 layer of surface hoar, facets, and some sun-crust on steep south aspects. Previous strong SW winds have formed windslabs in alpine and tree-line locations. The mid and lower pack is generally weak and faceted. Snow depths range from 50-80 cm at tree-line and up to 110+ cm in deeper alpine locations.

Weather Summary

The storm will bring more snow to the forecast area with another 10-20 cm possible overnight and into Thursday evening. Winds will switch to NE in the Banff area with an upslope finish to the storm. Freezing levels will hover around 1300 m then lower to valley bottom on Thursday. Winds stay in the light to moderate range.

For more information click Mountain Weather Forecast.

Terrain and Travel Advice

Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.
Storm slabs in motion may step down to deeper layers resulting in large avalanches.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.