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Avalanche Forecast

Archived

Jan 10th, 2023–Jan 11th, 2023

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

Regions

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

Continued low confidence in the overall snowpack structure is being felt by forecasters, despite recent benign weather and fewer natural and explosive-triggered avalanches of late. Increasing wind and warm temperatures on Thurs/Fri will likely contribute to worsening conditions.

Remain vigilant and settle in for a long winter of making conservative terrain choices to avoid negative interactions with avalanches.

Confidence

Moderate

Avalanche Summary

Forecasters from Mt. Norquay reported 2 size 3 deep persistent slabs on Mt Brewster that likely occurred on Tuesday afternoon. Lake Louise and Sunshine had limited results. The Visitor Safety field team did not observe any avalanches and experienced limited whumphing despite traveling through (low angle) rocky terrain.

Snowpack Summary

10-20 cm of recent storm snow sits over a denser mid-pack which has formed a slab over the weak facet layers below. The December 17 persistent layer of surface hoar/facets is down 25-60 cm and becoming less reactive. The November 16 deep persistent layer of facets, depth hoar, and/or sun crusts is found near the base of the snowpack with test results continuing to show sudden failures. Puzzle Peak snow profile today.

Weather Summary

On Wednesday, clear in the morning, with increasing clouds in the afternoon. No precipitation. Valley temperatures are about -4 and the ridge about -10. Wind increasing to moderate/strong from the SW into the afternoon.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Use careful route-finding and stick to moderate slope angles with low consequences.

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.