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Avalanche Forecast

Archived

Jan 1st, 2023–Jan 2nd, 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.

Current conditions are complex and very uncertain. A big-picture approach using avoidance of terrain features with wide margins is necessary.

Human-triggered avalanches are likely in any avalanche terrain where a slab sits over the deeper facet layers. Be watchful for remote triggers from greater than anticipated distances.

Trying to outsmart this condition will likely not end well. Backcountry users need to maintain discipline for the coming weeks and perhaps months.

Confidence

Moderate

Avalanche Summary

A skier-triggered size 2 avalanche in the Emerald Lake slide path occurred Saturday on the basal facets resulting in life-threatening injuries.

Mostly size 1 results from control at local ski areas. A flight today in the Lake Louise area showed avalanches up to size 3 but likely 48+ old. Extensive whumping and remote triggers of very small features below tree-line in Little Yoho today.

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

Warmer than seasonal temperatures (close to zero in the valley and -5 at the ridge) is expected Monday and Tuesday. Wind speed is a bit uncertain but ranges from light to moderate from the NW. With the warm temps come clearing into Monday with no precipitation.

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.