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Avalanche Forecast

Archived

Apr 21st, 2023–Apr 22nd, 2023

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

Regions

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

Although we’ve entered spring, we still have a winter snowpack with a weak basal structure. The only way to reduce risk when dealing with the basal weak layer is avoidance.

Confidence

Moderate

Avalanche Summary

A few small natural loose dry avalanches were noted along the highway corridor Friday. No new slab avalanches were observed or reported today.

Snowpack Summary

A new surface crust has formed on solar aspects to ridge crest. On northerly aspects, up to 40cm of recent storm snow remains preserved. Multiple buried crusts are present in the mid-pack on solar aspects. The basal snowpack remains weak with facets and depth hoar.

Weather Summary

A trough of low pressure will form over the forecast region bringing cloud cover and light precip. A mix of snow and rain will fall at the valley bottom as freezing levels climb to 2200 through the day. Minimal accumulation is expected over higher terrain. Winds will remain in the light to moderate range in the alpine.

Terrain and Travel Advice

  • Avalanche hazard may have improved, but be mindful that deep instabilities are still present.

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.

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.