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Avalanche Forecast

Archived

Dec 13th, 2024–Dec 14th, 2024

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.

Areas east of the divide have a weaker, thinner, more facetted snowpack, while areas along the divide and further west have a slightly thicker snowpack that is more supportive and a little more confidence inspiring. At lower elevations in all areas the snowpack is still thin with difficult travel and early season hazards present.

Confidence

Moderate

Avalanche Summary

No new avalanche observed or reported on Friday. Over the past several days, ski hills have triggered isolated wind slabs and a number of deep persistent avalanches with explosives, but there has been an improving trend.

Snowpack Summary

Old windslabs exist in wind-prone alpine areas. In sheltered locations, 10-40 cm of soft snow sits on a layer of facets, suncrust and isolated surface hoar. Below this the midpack is thin, facetted and weak in eastern areas; and deeper and denser in western areas. Two crust/facet layers exist near the bottom of the snowpack (Nov. 9th and Oct. 20th interfaces). Total snowpack depths at treeline are about 60 cm in eastern areas with up to 100 cm in thicker western areas.

Weather Summary

Moderate to strong SW/W winds, treeline temperatures between -8 and -5°C, and only a trace of new snow for Saturday.

An upper trough and system from BC/Washington will move in Saturday. Southwest and west ridgetop winds will increase, west winds through the valleys will dominate and some flurries are expected Saturday, mainly on the western most slopes.

Terrain and Travel Advice

  • Wind slabs are isolated, but may remain reactive.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and slopes above cliffs.

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.