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Avalanche Forecast

Archived

Jan 19th, 2023–Jan 20th, 2023

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 snowpack remains generally shallow and weak with a few deeper areas found to the west of the region.

Although the upper snowpack may be starting to "feel" more supportive, bear in mind that what you are feeling are effectively surface slabs that overlie weak, very unsupportive, faceted snow. This structure is not to be trusted.

Stick to low consequence terrain.

Confidence

Moderate

Avalanche Summary

No new natural activity observed today. The Lake Louise avalanche control team triggered another deep persistent slab on a S aspect at treeline with explosives yesterday (sz 1.5). They also found fresh windslabs this morning in immediate lees. These were generally 10-15cm, but up to 30cm deep, and propagated fairly well : up to 60m wide.

Snowpack Summary

Dribs and drabs of snow over the past 2 weeks have amounted to 10cm. This sits on a surface hoar /crust layer which is sporadic in the region. The Dec 17 surface hoar/sun crust layer is down 25-50cm, and generally not reactive. The Nov. 16 deep persistent layer is down 40-90cm and continues to produce sudden failures in snowpack tests. In Little Yoho, these two layers are deeper and more spread apart in the snowpack.

Weather Summary

West to NW winds Friday evening with alpine Temperatures -10 to -15C. Saturday an upper trough moves through the region bringing light accumulations of snow north of Lake Louise with west winds and freezing levels near valley bottom. Saturday night a cold front will pass bringing 5cm , northwest winds and alpine temperatures near -10C. Ridgetop winds will remain 20-40km/hr for the period.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.

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.