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Avalanche Forecast

Archived

Nov 17th, 2023–Nov 18th, 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.

Avalanches failing on the ground can be triggered by recreationalists this weekend on approach slopes to ice climbs, between pitches, or on slopes that look inviting to ski.

Early Season Conditions persist.

Confidence

Low

Avalanche Summary

In the past 48 hrs, several natural avalanches to size 2.5 failing to ground were reported by both Sunshine and Lake Louise ski hill's. On Friday, several avalanches were triggered by ski cuts or explosives. Lots of whumphing and shooting cracks was reported with one slope triggered from 10 m away which then propagated 60-70 m wide.

While we have limited observations, ski hills are reporting slabs that are very sensitive to human and natural triggers.

Snowpack Summary

It's still very much early season. With 30-50 cm at tree line and 50-80 cm in the alpine. Many early season hazards LURK below the snow's surface.

Wind & persistent slabs at tree line and in the alpine have been sensitive to human triggering and also failed naturally. Once triggered, failures have stepped to ground running on facets/intermittent early season melt freeze crust.

Forecasters are still working with limited observations.

Weather Summary

On Saturday, temperatures will again be mild. Freezing levels are forecasted to climb to 2100 m for slopes furthest East of the Divide. Winds will be moderate SW and skies will be a mix of sun and cloud.

For more info, please see the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • 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.

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.