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Avalanche Forecast

Archived

Dec 25th, 2023–Dec 26th, 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.

Watch for wind loading at ridgetops, and use caution in wind-loaded features or areas with weak basal facets. These problems are still sensitive to human triggering.

With long nights and cold temperatures on deck, be ready for any unexpected delays.

Happy Holidays from the Banff Visitor Safety Team!

Confidence

Moderate

Avalanche Summary

Wind loading and the deep persistent facets contributed to a close call near Bow Summit on Dec 23rd.

Over the past couple of days ski hill snow safety teams reported a few size 1-1.5 wind slabs as a result of explosives and ski-cutting work in alpine features and there were a few natural small wind slabs and wind-triggered loose dry avalanches in the alpine.

Snowpack Summary

Newly formed wind slabs can be found in lee aspects at treeline and in the alpine. 5-10 cm of snow sits over the Dec 22 melt-freeze crust that extends to ~1900 m. 15-50 cm of snow sits over the Dec 5 crust that exists to ~2300 m, and is more prevalent in the southern part of the forecast area. The base of the snowpack is a mix of weak facets, depth hoar and a decomposing Oct crust. Low elevations consist of a re-frozen previously wet snowpack.

Treeline snow depths range from 50-95 cm.

Weather Summary

Tuesday will be mainly cloudy with scattered flurries leading to trace accumulations. Strong to extreme southwest winds at ridgetop shifting to become west-northwest later in the day. Freezing levels at or near valley bottom.

The overnight low in the alpine is expected to be about -6°C and drop to -10°C during the day.

For more information, click Mountain Weather Forecast.

Terrain and Travel Advice

  • Be especially cautious as you transition into wind affected terrain.
  • Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
  • Early season avalanches at any elevation have the potential to be particularly dangerous due to obstacles that are exposed or just below the surface.

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.

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.