Avalanche Forecast

Issued: Dec 9th, 2013 7:36AM

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.

Avalanche Canada rbuhler, Avalanche Canada

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 with sunny breaks possible, light snow flurries, treeline temperatures around -15C, light to moderate NW alpine winds switching to SW overnightWednesday: Light snow flurries, treeline temperatures -10 to -15C, light to moderate SW alpine winds Thursday: Light snowfall, treeline temperatures around -10C, light to moderate SW alpine winds

Avalanche Summary

On Sunday two natural wind slab avalanches were reported around Revelstoke: a size 1.5 on a steep SE aspect at 2000m and a size 2.5 on a N aspect. Also reported in the area was a size 2 skier triggered persistent slab avalanche releasing on the late-Nov interface on a north aspect 40 degree slope at 1900m.Two ski cut avalanches reported on Saturday around Revelstoke. One size 1.5 storm slab on a NE aspect and one size 1 wind slab on a SW aspect at treeline.

Snowpack Summary

Snowpack depths are typically 100-140 cm at treeline elevation. 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 (~30-60cm) 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. The October crust can be found in the alpine on north aspects and the early November surface hoar is isolated within the region.

Problems

Wind Slabs

An icon showing 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.
Be cautious as you transition into wind affected terrain.>Avoid travelling in areas that have been reverse loaded by winds.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

An icon showing 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.
Caution around convexities or large, unsupported slopes>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

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