Avalanche Forecast

Issued: Dec 8th, 2012 9:12AM

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

mbender, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Poor - Due to limited field observations for the entire period

Weather Forecast

Sunday: Moderate to heavy precipitation throughout the day with strong gusting to extreme northwesterly winds. Alpine temperatures -3 degrees with a freezing level at 1000m. Monday: Heavy precipitation with southwesterly winds 30-50km/h gusting to 90km/h. Freezing levels expected at 800m with alpine temperatures -4 degrees.Tuesday: Light precipitation, temperatures cooling to -7 in the alpine. Winds southwesterly moderate to strong.

Avalanche Summary

Natural activity isolated to the storm snow to size 1.5. Explosives testing north of the Stewart region indicate an avalanche running to size 3.5 in north facing alpine terrain failing in a weak layer of facets near the base of the snowpack.

Snowpack Summary

The storm snow from the past week has settled and been redistributed by the wind from a variety of directions at upper elevations. Alpine and treeline surface snow conditions are variable with buried wind slabs, newly formed wind slabs and areas that are heavily scoured. The mid-pack is gaining strength and is well settled.An November facet/crust layer can be found in the bottom quarter of the snowpack. We do not have much recent information on this facet/crust interface, so it may be worth digging down yourself to test its reactivity.Total snowpack depth above 1000 m is 150-200 cm deep. Below 1000 m the snowpack shows a sharp transition from 100 cm dropping to 50 cm, and is generally below threshold.

Problems

Wind Slabs

New snow combined with forecasted strong northwesterly winds will have created windslabs in the lee of terrain features. Strong winds often create slabs further down the slope than expected and in open areas below treeline.

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: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Deep Persistent Slabs

Deeply buried facet/crust weaknesses are prone to remote triggering and step down avalanches. Typical trigger points include thin rocky areas. They may be difficult to trigger, but deep persistent slab avalanches are often very large and destructive.

Carefully evaluate and use caution around thin snowpack areas.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 6

Valid until: Dec 9th, 2012 2:00PM