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Avalanche Forecast

Archived

Feb 9th, 2012–Feb 10th, 2012

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

Regions

Kootenay Boundary.

Confidence

Good - -1

Weather Forecast

A series of weak frontal systems are expected to bring light amounts of fresh snow to the region on Friday, and trace amounts for Saturday and Sunday, but the timing is uncertain. Winds are expected to be generally light southwesterlies, but winds associated with snow squalls could get quite gusty. Freezing levels should remain in valley bottoms but could rise above 1000m with the passage of warm fronts.

Avalanche Summary

Fresh hard wind slabs on west through northeast aspects are very touchy with recent natural and skier-triggered avalanches up to Size 2. Loose faceted surface snow is sluffing readily in steep terrain and gaining considerable mass. Deep persistent slab avalanches remain possible with heavy triggers in shallow rocky snowpack areas on unsupported slopes. Check out the Avalanche Image Gallery under the Library tab for some photos of recent deep persistent slab avalanches in the region.

Snowpack Summary

Light amounts of fresh snow has buried the previous snow surface which includes surface hoar up to 30mm at ridgetop and 50mm in valley bottoms, 30cm of near-surface facets on shady sheltered slopes, and surface crusts on sun-exposed slopes. Exposed alpine and treeline areas are wind-affected and variable with scoured areas and pockets of hard wind slab. Concerns remain for the mid-December persistent weakness down around 80-100cm. Basal facets were recently responsible for a large whumpf on a shallow south facing treeline slope in the Rossland Range and gave very easy and sudden compression tests results where they were found down 60cm.

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.

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.