Avalanche Forecast

Issued: Dec 23rd, 2012 9:09AM

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

pgoddard, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Due to variable weather conditions

Weather Forecast

Monday: Light S winds, with moderate to strong NE outflow winds in places. Alpine temperatures around -11 with an inversion (colder temperatures in the valley floor). Â No precipitation.Tuesday: Light winds. Alpine temperature around -9 with an inversion. No precipitation.Wednesday: Light S winds. Alpine temperature around -10. No precipitation.

Avalanche Summary

On Saturday, several natural size 1-2 loose dry and thin slab avalanches failed in steep isolated terrain features wind-loaded by outflow (down-valley) winds. Explosives triggered size 2-3 slabs which failed near the ground in facets. Near Bear Pass, natural ice fall triggered size 2.5 and 3 loose snow avalanches, entraining old storm snow.

Snowpack Summary

Wind slabs and cornices have developed on a fairly widespread basis and may be found in unusual locations lee to NE and E outflow winds. Surface faceting is likely to continue while the weather remains cold. A layer of surface hoar buried in the upper metre of the pack has been observed in the Shames backcountry. The midpack is generally well settled. Near the base of the snowpack, a crust/facet layer continues to give hard, sudden results in snowpack tests. This weakness is unlikely to be triggered by a single person, but it remains possible with a very heavy load (e.g. cornice fall) or from a thin-spot trigger point.

Problems

Deep Persistent Slabs

A deeply buried weakness may be triggered from thin, rocky snowpack areas or with a large trigger.

Avoid thin, rocky or sparsely-treed slopes.>Be aware of thin areas that may propagate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 7

Wind Slabs

New wind slabs have formed in response to down-valley winds. These could be triggered by the weight of a person or snowmobile.

Avoid travelling in areas that have been reverse loaded by winds.>Stay well to the windward side of corniced ridges.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Valid until: Dec 24th, 2012 2:00PM