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Avalanche Forecast

Archived

Nov 24th, 2011–Nov 25th, 2011

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Kootenay Boundary.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain

Weather Forecast

Moderate amounts of snowfall are forecast overnight. Friday conditions look dry with sunny periods. Freezing levels are expected to rise Friday afternoon up to 1000m then lower to valley bottom. Saturday afternoon freezing levels could rise to 2000m with snow to follow late in the afternoon or Saturday night. Sunday freezing levels could rise again 2000m accompanied by moderate to heavy snowfall.

Avalanche Summary

Several natural avalanches have been reported from the southern part of the region. These range in size anywhere from size 1.0-2.0 between 1900-2000m on southeast aspects. Avalanche control work also produced avalanches up to size 2.5 on southeast-southwest aspects between 1900-2100m. This information is from a portion of the region and avalanche activity may differ with size, aspect, and elevation around your local mountains.

Snowpack Summary

In upper elevations an average up to 70cm of new snow has fallen in the southern part of the region creating storm slab instabilities. This has been accompanied by moderate to strong winds from the southwest which are responsible for forming new wind slabs in the alpine and at treeline below ridgelines and terrain features. At treeline I suspect there to be some patchy areas of buried surface hoar and older raincrusts buried lower in the snowpack potentially up to a meter deep. With very limited observations from the field I suspect these layers (if existing) have or will reach their threshold and become reactive. I sense these layers will either clean themselves out, or start a healing process. Snowpack depths are likely in the 60-90cm range at about 1600m and up to 150cms at 2000m. This is a good time to sit out the storms and let the snowpack settle. There is a new post in the forecaster's blog, which is located at the bottom of the bulletin. The post entails "Post Storm Risk Management Strategy" written by Karl Klassen. Check it out, and let us know what you think.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.