Avalanche Forecast

Archived

Jan 11th, 2019–Jan 12th, 2019

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 possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Banff Yoho Kootenay.

The recent storm snow is settling rapidly with warm temps and contributing to the significant slab sitting over weak basal facets and depth hoar. Warm temps will keep these slabs sensitive to human triggering in the thinner snowpack areas.

Weather Forecast

Freezing levels are forecast to approach 2200m daily through Monday which may keep slabs sensitive to human triggering. Watch for potential temperature inversions. Moderate to Strong SW winds should start to diminish Saturday and it looks to be cloudy near the divide until Monday when the potential for solar inputs looks likely.

Snowpack Summary

Snowfall since Jan2 has been redistributed by southwest winds yielding extensive wind effect in the alpine. In thick snowpack areas, the Dec 10th weak layer of facets is now down 100-150cm with a stronger snowpack below. In thin snowpack areas, there is little separation between Dec 10 and the weak depth hoar/ facets sitting 40 cm above the ground.

Avalanche Summary

A group just outside of the Lake Louise ski area above the Pika Flats at treeline triggered a sz 2 slab 80cm deep failing 40m wide and running 200m on a SW aspect today. The snow safety team at Sunshine Village saw several windslabs fail in the last 24 hrs one of which scrubbed to the ground and produced a large avalanche off of the Monarch.

Confidence

Freezing levels are uncertain on Saturday

Problems

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.

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.