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Avalanche Forecast

Archived

Nov 25th, 2022–Nov 26th, 2022

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

Regions

Lake Louise.

A classic Rockies snowpack is starting to form with a weaker base and slabs on top. While winds remain elevated and new snow accumulates, ice climbers and gully skiers should consider the potential for heavy sluffing. We have significant uncertainty due to minimal field observations.

Confidence

Moderate

Avalanche Summary

Some smaller slabs were noted at the Lake Louise ski hill but limited visibility overall. A notable size 2 wind slab was remotely triggered 2 days ago on Observation Sub Peak. It had impressive propagation on the underlying weak facets and scrubbed to the ground. Not in Banff, but an ice climber close call on Thursday with loose dry avalanches on Shades of Beauty in Jasper is very relevant to our area.

Snowpack Summary

5-15cm over the last 24 hours (higher amounts West of the divide and in the North). Strong to extreme SW winds and warm temperatures over the past 36 hours have promoted wind slab growth at higher elevations (10-30cm thick have been observed). The snowpack below these slabs is a mix of facets, some spotty surface hoar, and sun crust on steep south aspects. There is even some classic Rockies depth hoar forming at the base in thinner areas. 40-80 cm of total snow exists at treeline throughout the region, with up to 120 cm in loaded alpine features.

Weather Summary

5-10cm overnight and moderate winds. A warm front on Saturday with flurries and 40-50kmh ridgetop SW winds, increasing to 60 kmh in the afternoon. Expect freezing levels to 1400m.

On Sunday, a cold front with 5-10cm in Lake Louise and Yoho areas, and lesser amounts (5cm) in the rest of the regions. Expect continued strong winds and valley bottom freezing levels.

For more information specific to the forecast region, see https://avalanche.ca/weather/forecast

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for areas of hard wind slab on alpine features.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Loose avalanches may start small but they can grow and push you into dangerous terrain.

Problems

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.

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.

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.