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Archived

Avalanche Forecast

Dec 9th, 2012–Dec 10th, 2012
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Northwest Coastal.

The Danger Ratings are based on precipitation amounts forecast for the southern portion of the region.

Confidence

Poor - Timing, track, or intensity of incoming weather is uncertain for the entire period

Weather Forecast

Monday: Moderate precipitation with westerly and southwesterly winds 30-50km/h gusting to 90km/h. Freezing levels expected at 600m with alpine temperatures -5 degrees.Tuesday: Light to locally moderate precipitation, temperatures cooling to -7 in the alpine. Winds southwesterly moderate to strong.Wednesday: Light flurries, winds light from the northwest and alpine temperatures -6.

Avalanche Summary

Natural activity isolated to the storm snow to size 1.5. Explosives testing in the past few days 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

An additional 15-30cm of snow has fallen accompanied by strong winds. This sits on top of the settled storm accumulations from last week. 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.A November facet/crust layer can be found near the base of the snowpack. We don 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 160-220 cm deep. Below 1000 m the snowpack shows a sharp transition from 100 cm dropping to 50 cm, and is generally below threshold.

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

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.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely

Expected Size: 2 - 6