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 8th, 2024–Dec 9th, 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.

A sensitive weak layer (Dec 7) has just been buried by the recent storm snow. The new snow is bonding poorly to this interface, yet no widespread avalanche cycle was observed. The surface snow mostly remains cold and dry, but in locations where the wind has created a surface slab, watch out as these spots will be easily triggered.

Confidence

Moderate

Avalanche Summary

Good visibility on Sunday and most reports have not observed much in the way of fresh avalanches except where you would expect them. Several storm avalanches up to size 2 out of steep terrain on Bow Peak (Grandaddy area), several small storm slabs at the LL and SSV ski areas, but no large natural avalanches reported in the backcountry (yet).

Snowpack Summary

Storm snow totals of 23-32 cm fell across the region, sitting on a freshly buried weak layer (Dec 7) that will be the one to watch for a few days. This new snow won't bond well to Dec 7 (facets and crust), and the key will be to watch for slab development in the surface layers - wherever the wind has stiffened up the snow, watch for an easily triggered windslab. Any avalanches starting in the surface layers have the potential to step down to the facets near the ground.

Weather Summary

The weekend storm has passed, followed by a clearing trend as a ridge of high pressure moves over the area, cools the air and stabilizes the weather for a few days. Monday and Tuesday should be mostly clear with few clouds, light winds and high temperatures of -7. Another system offshore should change this pattern by the second half of the week.

Terrain and Travel Advice

  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.