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Avalanche Forecast

Archived

Nov 20th, 2012–Nov 21st, 2012

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

Jasper.

Highly variable snow distribution across forecast area. Evaluate each slope carefully.

Weather Forecast

There are two distinct weather systems over our forecast area. To the north, cold temperatures (-16) and light flurries are expected for the next two days. South of the Columbia IcefieldĀ  a much milder air mass has produced 30+ cm of snow.

Snowpack Summary

There are a variety of layers in the snowpack that relate to the early season snow, rain and freeze-thaw cycles. These can be consistently found in field tests but the depth of the weaknesses and the type of shears vary from slope to slope.

Avalanche Summary

Several natural avalanches to size 2.5 were observed today. All the slide activity seems to be wind slabs on steep lee and cross loaded slopes in the alpine.

Confidence

Timing, track, or intensity of incoming weather system is uncertain

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.

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.