Avalanche Forecast

Archived

Dec 25th, 2013–Dec 26th, 2013

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

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 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.

Regions

Cariboos.

Expect avalanche danger to increase throughout the day. Danger may be lower in areas that receive less snowfall than forecast.

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Synopsis: A series of frontal systems pushing across Northern BC will bring moderate to heavy precipitation to the Caribous Tonight through Friday. Saturday will see a return to relatively cool and dry conditions in the wake of the storm.Tonight and Thursday. Snow amounts: 20-40 cm. Ridge winds: Strong westerly. Freezing levels: Rising to 1500m.Friday. Snow amounts: Up to 10 cm. Ridge winds: Strong westerly. Freezing levels: 1200m.Saturday: Flurries. Ridge winds: light northwesterly. Alpine temps: -10.

Avalanche Summary

We've received recent reports of the basal weaknesses causing large natural avalanche to ground on N to NE aspects.Reports of avalanches on the early December surface hoar from the Monashees where the snow amounts of the last storm were greater suggest that we may see a similar cycle develop in the Caribous over the next couple of days.

Snowpack Summary

We're dealing with a complex snowpack in the Caribou Mountains at this time. New snow will load the regions persistent weak layers which could reach a critical point tomorrow.Up to 160cm of snow can be found at treeline. Alpine snow depths vary between 1 to 2m. New snow is falling on a settling upper snow pack. 50 to 80cm of snow now sits on a variety of old weak layers from early December: surface hoar, faceted snow, and/or a crust. Previously warm temps have formed a cohesive mid pack on top of surface hoar or facets from late November. Snowpack tests results have been varied but some are showing this layer pop with medium loads. 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.

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.