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Avalanche Forecast

Archived

Feb 16th, 2023–Feb 17th, 2023

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

Regions

North Rockies, Kakwa, McGregor, Pine Pass.

New snow and moderate to strong winds are building touchy wind slabs at treeline and alpine elevations. Conservative terrain travel is recommended.

Confidence

Moderate

Avalanche Summary

Natural and human-triggered size 1 to 1.5 wind slabs were reported in the Pine Pass area.

Looking forward, new wind slabs are likely to form directly lee of ridges and ribs. These new wind slabs are forming over old wind slabs that are generally bonding to previous surfaces but may be triggered by large loads like a cornice.

The lower snowpack is slowly gaining strength, continue to manage this problem by avoiding terrain that is steep, rocky, and shallow.

Snowpack Summary

Roughly 20 to 30 cm of new snow with the greatest amounts near Pine Pass is being redistributed by moderate southwest winds. New wind slabs in open terrain at all elevations will remain reactive for the near future. Cornices are becoming overhanging and reactive, and new snow and wind will further develop their growth.

The mid-pack is gaining strength and consists of rounding facets and melt-freeze crusts that are starting to degrade.

Near the base of the snowpack, a persistent weak layer composed of large and weak facets formed in November is strengthening slowly. This layer is most likely to be triggered in thin, rocky alpine and upper treeline terrain.

Weather Summary

Thursday night

Cloudy with snowfall tapering overnight, trace accumulation, 40 to 50 km/h southwest winds, treeline temperatures -12 °C.

Friday

Cloudy with flurries, increasing snowfall overnight accumulation 10 to 15 cm, 30 to 40 km/h southwest winds, treeline temperatures -10 °C.

Saturday

Cloudy with flurries easing in the afternoon, accumulation 5 to 10 cm, 30 to 40 km/h southwest winds, treeline temperatures -10 °C.

Sunday

Cloudy with snowfall, accumulations of 10 to 15 cm, southwest winds 40 to 50 km/h, treeline temperatures -10 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid exposure to slopes that have cornices overhead.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

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.