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Avalanche Forecast

Archived

Jan 6th, 2025–Jan 7th, 2025

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

Regions

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

Change is coming as a notable period of calm weather comes to an end.

Be aware of increasing winds on Tuesday: these winds are expected to increase natural avalanche activity in the region.

Confidence

Moderate

Avalanche Summary

A field team on a flight with perfect visibility throughout Banff, Yoho and Kootenay observed a few natural size 2 windslabs in lee alpine terrain and a cornice failure that ran further than expected.

Snowpack Summary

10-20cm of low-density snow overlies a weak, faceted, mid and lower snowpack. This surface snow will be transported easily by incoming winds, so expect slab development as the winds pick up on Tuesday. At the bottom of the snowpack, weak depth hoar and facets associated with old crusts are found. An average of 60-100cm of snow can be found at treeline elevations.

Weather Summary

The story of the next few days is wind. After a period of very calm conditions, the winds are forecasted to increase throughout the day on Tuesday. Expect strong to extreme ridgetop winds overnight on Tuesday and Wednesday. Temperatures will remain cold (-5 to -15 at treeline) and minimal to no snow accumulation by Friday.

Terrain and Travel Advice

  • Avoid thin areas like rocky outcrops where you're most likely to trigger avalanches on deep weak layers.
  • Pay attention to the wind; once it starts to blow, sensitive wind slabs are likely to form.
  • Be careful with sluffing in steep terrain, especially above cliffs and terrain traps.

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

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.