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Avalanche Forecast

Archived

Dec 5th, 2022–Dec 6th, 2022

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

Regions

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

The persistent slab, hard windslabs and wind-affected snow conditions continue to be the story for the week as evidenced by Sunday's close call on Wolverine Ridge. The odd natural avalanche has occurred, but human triggering is likely on steep slopes.

Confidence

Moderate

Avalanche Summary

An explosive triggered a size 2 hard slab at Lake Louise, and a cornice fell and triggered a size 2 at Sunshine, both avalanches occurred in steep, alpine terrain. Yesterday a near-miss occurred in the Lake Louise backcountry with a persistent slab at treeline. Small sluffs of low-density surface snow should be expected in gullies.

Snowpack Summary

The snowpack surface is generally wind-blasted in most places with a few cm of low-density new snow from the past 24 hours. This has produced hard windslabs that can fail with the right trigger in the right place. Any avalanche triggered now will likely step down 20-40 cm into the persistent layers and become larger.

Weather Summary

An arctic ridge of high pressure over BC fights with a low-pressure system over Alberta, bringing cold temperatures and light snow for the next 24 hours. On Tuesday, expect 2-5 cm (more to the east), temperatures ranging from -10 to -15 and winds from the NW before a clearing trend for Wednesday.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for areas of hard wind slab on alpine features.

Problems

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.

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.