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Avalanche Forecast

Archived

Feb 14th, 2023–Feb 15th, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
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, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

Mt. Hector, Noseum, Silverhorn/Observation, and Bison avalanche closure zones on Highway 93N are CLOSED on Wednesday, February 15th for avalanche control.

Confidence

Moderate

Avalanche Summary

No new reports of natural or skier triggered avalanches on Tuesday. Lake Louise snow safety triggered a few thin windslabs to size 1.5 with explosives.

Over the past week there have been numerous natural, skier and explosive triggered avalanches to size 3, some with wide propagations an many stepping to ground.

On Monday, skiers triggered a size 2 windslab on the convex roll in Wawa bowl near Sunshine Ski area. Near Lake Louise ski area, in out of bounds bowl skiers triggered a size 2 windslab on a reload of a bed surface of basal facets from large avalanche on Dec 30. Avalanche control on Mt. Dennis and Mt. Field on Monday produced results up to size 3.

Over last weekend there were several notable avalanches. On Saturday, there was a MIN report of a remote-triggered slide with wide propagation in the Sunshine backcountry. On Sunday, a visitor safety team also triggered a healthy size 2.5 (80 wide) at 2400m on observation glades and another party on Helen Shoulder triggered a size 2.

Snowpack Summary

A mix of hard and soft slabs up to 50 cm deep lie on the surface due to last week's storm snow and extreme westerly wind. Non-wind affected areas have approximately 20 cm of soft snow on the surface.

The surface slabs sit on top of 30-60 cm over top of the January crust/facet interfaces and or firmer midpack layer from previous wind effect. The lower snowpack remains very weak and faceted.

Weather Summary

A ridge builds in the region, bringing clearer skies for Wednesday and Thursday. Light to moderate NW winds on Wednesday shift Thursday to moderate to strong Westerly winds as the ridge breaks down. Friday, expect light flurries (2-5 cm) with moderate to strong westerly wind. Alpine temperatures will range from -5 to -12C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Make conservative terrain choices and avoid overhead hazard.
  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.