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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

Little Yoho.

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

20-40 cm unconsolidated snow sits on the surface, waiting to be blown by incoming winds. The mid-pack is generally strong but a weak crust/facet layer can often be found near the ground, particularly in shallower areas. At treeline, average snowpack depths are 120-150 cm. The snowpack in Little Yoho is generally deeper and more consolidated than in areas further east in the BYK region.

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

  • Pay attention to the wind; once it starts to blow, sensitive wind slabs are likely to form.
  • Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.