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Avalanche Forecast

Archived

Dec 9th, 2013–Dec 10th, 2013

Alpine
Natural avalanches unlikely, human triggered possible.
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.
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 - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Unsettled conditions for the interior regions on Tuesday and Wednesday as the ridge of arctic air slowly breaks down. Seasonal conditions should return by Thursday and a low pressure system will move into the interior from the SW.Tuesday: Mostly cloudy, light snow flurries, treeline temperatures -10 to -15C, moderate NW alpine windsWednesday: Light snowfall, treeline temperatures around -10C, moderate NW alpine winds switching to SW during the dayThursday: Light snowfall, treeline temperatures -5 to -10C, light to moderate SW alpine winds

Avalanche Summary

We have received a report of several natural slab avalanches recently occurring south of Barkerville.  Slabs were typically 30-45cm thick (likely occurring on the late-November interface) and slid on East through West aspects.  Dimensions were typically 15-50m wide and running 15-75m in length.

Snowpack Summary

Snowpack depths are likely to be highly variable across the region, with elevation, and in wind-exposed areas. Low-elevation and wind-affected areas likely have a shallow faceted snowpack. In deeper areas, the upper snowpack (up to ~40cm) has undergone faceting during the recent cold temperatures. Small surface hoar has likely formed on the surface and is now buried by yesterday's snowfall.The old storm snow (~30-50cm) overlies the late-November interface which typically consists of sun crusts on steep south facing slopes and surface hoar in sheltered areas. These weak layers are expected to be persistent, although in many areas the upper slab is not yet stiff enough for slab avalanches. When temperatures rise, and we get additional snow, expect this interface to become more of a problem. Strong NE winds after the storm caused reverse loading and wind slab formation on SE through W aspects in wind exposed areas.Lower snowpack layers include a surface hoar layer roughly 60cm above the ground and an early season rain crust at the base of the snowpack. These layers have been inactive but residual risk of large, destructive avalanches exists, especially in areas with a thinner snowpack

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.