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Avalanche Forecast

Archived

Dec 10th, 2012–Dec 11th, 2012

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

Regions

Cariboos.

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

25-35 cm of snow is expected to fall on the Caribous until Tuesday accompanied by strong winds from the West. Later Tuesday and Wednesday, a ridge after the system should bring lighter winds and slightly cooler temperatures (-10 C). A weaker system is forecasted for Thursday leaving some light precipitation on the region and stronger winds. 

Avalanche Summary

A small natural slab avalanche has been reported on a West facing slope at 2200 m around Valemont yesterday. There are limited recent observations from this region.

Snowpack Summary

Strong winds from the South East and South West has created winds slabs on lee slopes yesterday. These winds slabs will continue to build with the forecasted moderate precipitation and strong winds from the West tonight and tomorrow. I suspect that they will be easy to trigger these windslabs with light loads in the alpine and at treeline. Sluffing (dry loose avalanches) is also a concern on steep slopes in wind sheltered areas. Average snow depths at treeline is between 160 and 220 cm. Elevations below 1500 m are still reported as below threshold. The deep persistent instabilities (surface hoar and early November crust) located in the middle and near the bottom of the snowpack are still a concern not so much because of their sensitivity but more because of the large size avalanches they would produce if they would be triggered. In general, snowpack information is sparse in this region and significant variations likely exist from one drainage to another. Digging down and making your own observations will be critical to safe slope selection. Any observations from the field are welcome at [email protected].

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.