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Avalanche Forecast

Archived

Nov 29th, 2014–Nov 30th, 2014

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

Little Yoho.

Natural activity has slowed down after the big storm, but conditions are prime for human triggering due to the deeper weak layers. Choose very conservative terrain. SH

Weather Forecast

Cold and clear on Sunday with temperatures in the mid minus 20's. We will see a slight warming trend through the forecast period and alpine winds shifting to a W/NW flow.

Snowpack Summary

Storm snow amounts over the last few days: 40cm in the Kootenay region, 50cm in the Lake Louise area, and 60 cm at Sunshine. 2 layers of concern, the Nov. 6th rain crust/facets 20-30cm above the ground, and the Nov 24th facet layer 25-50 cm above the ground. The new load of storm snow is overloading these layers.

Avalanche Summary

A natural cycle to sz. 3 on all aspects at treeline and above occurred during the storm. Explosive control at Sunshine and Lake Louise ski areas have been producing avalanches up to size 2.5. There is also extensive whumpfing at all elevations and aspects. A notable size 2.5 and size 2 were likely remote triggered in West Bowl in Lake Louise today.

Confidence

Due to the number of field observations on Saturday

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.