Avalanche Forecast

Issued: Jan 10th, 2013 8:37AM

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

pmarshall, Avalanche Canada

South Coast.

The presence of a buried weak layer requires discipline at this time. Start with small objectives and give the new snow a little longer to gain strength before pushing into more committing terrain.

Summary

Confidence

Good

Weather Forecast

Synopsis: A ridge of high pressure should be the dominant feature over the next several days. The only exception is on Saturday when a weak disturbance moves across the coast. Inland areas of the coast may only see a bit more cloud from this pulse. Temperatures should stay slightly below normal with daytime highs around -10 at treeline and winds generally light from the north. The sun should return on Sunday with temperatures starting to rise and the potential for an above freezing layer to form.

Avalanche Summary

There are reports of a widespread natural avalanche cycle from Tuesday night and Wednesday. Slab avalanches up to size 3 were observed, with many events occurring below treeline and failing on the early January surface hoar layer. There are also a couple reports of skier triggered avalanches up to size 2 and avalanches being triggered from a distance.

Snowpack Summary

40-80 cm of snow fell earlier this week, with the heaviest amounts in the Coquihalla area. Strong southwesterly winds produced dense wind slabs in exposed leeward terrain. Weaknesses exist within this recent storm snow as well as at the interface with the previous snow surface, which includes large surface hoar, facets, old hard wind slabs, or a sun crust. Recent compression tests on a north aspect below treeline gave several sudden planar (pops) results in the top 100 cm. No significant weaknesses have been reported recently below this in the mid snowpack layers. Near the base of the snowpack, a crust/facet layer exists, which is now unlikely to be triggered, except perhaps by heavy triggers in steep, shallow, rocky terrain where more facetting has taken place.

Problems

Persistent Slabs

Up to 80 cm of snow sits on a weak layer consisting of surface hoar, a crust, and/or sugary facets. This weakness may be triggered by light loads, from a distance, and in relatively low angle terrain.

Choose conservative lines and watch for clues of instability.>Remote triggering is a concern, watch out for adjacent slopes.>Be wary of slopes that did not previously avalanche - even on low angle terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 5

Wind Slabs

Deep and dense wind slabs are likely behind ridges and terrain breaks.

Use ridges or ribs to avoid pockets of wind loaded snow.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Valid until: Jan 11th, 2013 2:00PM