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Avalanche Forecast

Archived

Nov 18th, 2023–Nov 19th, 2023

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

Regions

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

The avalanche hazard may increase slightly on Sunday as more wind loading occurs. Avalanches failing near the ground on a persistent weak layer can be triggered by people on steep slopes around ice climbs, or areas that look inviting to ski.

Early Season Conditions persist.

Confidence

Moderate

Avalanche Summary

Local ski hills and recent backcountry observations have reported lots of whumphing, shooting cracks and avalanches up to size 2+ in steep treeline and alpine terrain. These avalanches have been very sensitive to human, natural and explosive triggers. There have also been reports of remotely triggering avalanches from significant distances. Most of these avalanches are failing on a layer of facets and/or a melt-freeze crust near the bottom of the snowpack.

Snowpack Summary

It's still very much early winter with only 30-50 cm at tree-line and 40-80 cm in the alpine. Many early season hazards lurk just below the snow surface.

Recent winds have helped form slabs which sit over weak basal facets and/or a buried melt-freeze crust near the base of the snowpack. This persistent weak layer will be present for the foreseeable future.

Weather Summary

Some light flurries are possible on Saturday night and into Sunday, especially in areas west of the divide. No significant accumulations are expected. Winds will increase into the strong range, 40-60 km/hr, out of the west. Freezing levels will be around 1500 m in the east and 1400 m in the western areas.

For more info, please see the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Ice climbers should be equipped with avalanche safety gear.

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.