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Avalanche Forecast

Archived

Dec 31st, 2022–Jan 1st, 2023

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

Human-triggered avalanches are likely in any avalanche terrain where a slab sits over the deeper facet layers. Remote triggering of these weak layers is also possible.

This is not a problem you can outsmart and it will linger for the foreseeable future. The ways to reduce risk are through avoidance of avalanche terrain or choosing small slopes where the consequences of an avalanche will be smaller.

Start the New Year with patience and wait for things to improve.

Confidence

High

Avalanche Summary

A skier triggered size 2 avalanche in the Emerald Lake slide path occurred Saturday on the basal facets resulting in serious injuries. Several other human triggered and remotely triggered slabs on this basal interface from size 2-2.5 have also occurred in the past three days. Avalanche explosive control over the last week produced large avalanches up to size 3 in many different areas on 95% of the shots. Some were initiated on the Dec. 17 interface but most stepped down to the basal facets.

Snowpack Summary

10-20 cm of soft surface snow in sheltered areas. Below this a settled slab 25-60 cm thick sits over a weak layer of facets and surface hoar from Dec 17. Below this another 20-40 cm of facets sit over the weak Nov 16 interface, with the bottom 20-50 cm of the snowpack made up of weak facets and depth hoar. Total snowpack depths of 80-140 cm at treeline.

Weather Summary

Some light flurries overnight into Sunday with a few cm's of accumulation in the West near the divide. Sunday should be a mix of sun and cloud. Winds will be in the moderate range from the W-NW becoming light on Sunday. Temperatures will remain steady in the -10 to -14°C range.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.