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Avalanche Forecast

Archived

Dec 14th, 2020–Dec 15th, 2020

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
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.

Wind and new snow are approaching the forecast region. Expect to see wind slab development in the alpine. Continue to watch for sluffing of surface snow in steep terrain, especially steep gullies.

Weather Forecast

The wind is supposed to pick up to the strong range on Tuesday, from the SW. Temperatures will remain steady at -15 at the ridge and about -10 in the valley. Snow is expected to start midday Tuesday and continue through until Thursday, the amount totaling about 20cm over the 3 days.

Snowpack Summary

From trace to 10cm new snow and light wind effect in the alpine. 20-40 cm of faceted snow sits on the Dec 7th layer of sun crust, facets or surface hoar depending on your location. The Nov. 5th crust / facet layer persists at the bottom of the snowpack and continues to weaken over time. Snowpack depths are 90-160cm at tree line.

Avalanche Summary

Both Sunshine and Lake Louise ski patrollers report small wind slabs up to size 1.5 at the largest, through a combination of explosive work and ski cutting.

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Tuesday

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.

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.

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.