Avalanche Forecast

Issued: Dec 9th, 2013 7:34AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Persistent Slabs.

rbuhler, Avalanche Canada

Cariboos.

Summary

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

Northerly outflow winds have reverse-loaded and cross-loaded exposed slopes forming wind slabs below ridge crests and behind terrain features. Don't let wind slabs in unusual places catch you by surprise.

Avoid freshly wind loaded features.>Avoid traveling in areas that have been reverse-loaded or cross-loaded by winds.>

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

Managing these persistent slabs can be tricky; they are stubborn and direct evidence of unstable snow may be lacking, but they can produce very destructive avalanches. Treat large open slopes with suspicion until stability is confirmed.

Use extra caution in areas with a thin or variable snowpack.>Use extra caution around convexities or large unsupported slopes.>Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Dec 10th, 2013 2:00PM