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Avalanche Forecast

Archived

Dec 26th, 2013–Dec 27th, 2013

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

Cariboos.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Friday: Moderate snowfall 10-15 cm. The freezing level is around 1200-1400 m and winds are moderate gusting strong from the southwest. Saturday: Mainly cloudy with a chance of flurries and possible sunny breaks. The freezing level drops to around 800-1000 m and winds are moderate from the northwest. Sunday: Mainly cloudy with a chance of flurries or light snow. The freezing level is near valley bottom.

Avalanche Summary

We've received recent reports of the basal weaknesses causing large natural avalanche releasing on or near the ground on N to NE aspects. Human triggering of large destructive avalanches is possible at this time.

Snowpack Summary

An additional 20 cm of snow has fallen accompanied by moderate to strong W-SW winds and mild temperatures. New dense wind slabs are likely in exposed lee terrain at and above treeline. Up to 80cm of snow now sits on a variety of weaknesses from early December (surface hoar, faceted snow, and/or a crust). An older layer of surface hoar or facets from late November can be found deeper in the snowpack. Recent snowpack tests results vary but some are showing this layer "pop" with medium loads, indicating a potential for human triggering.Snowpack depths vary, but in general up to 150 cm of snow can be found at treeline, with 100-200 cm in the alpine. In many places we're still dealing with a relatively thin snowpack so there's not a whole lot of snow between riders and the sugary snow (facets) near the ground. A facet/crust combo has been recently active in parts of the region.

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.

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.

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.