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Archived

Avalanche Forecast

Dec 11th, 2015–Dec 12th, 2015
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
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
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
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
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
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 Inland.

I'm uncertain about the distribution of a layer of buried surface hoar at and around tree-line. If it is more widespread than I suspect then danger ratings may be greater than forecast.

Confidence

Low - Due to the number of field observations

Weather Forecast

SATURDAY: Flurries, light southwest winds, freezing levels at the valley floor, SUNDAY: light flurries mainly south of HWY16, moderate east winds, -10 at 1000m. MONDAY: mainly clear, light northwest winds, -10 at 1000m.

Avalanche Summary

There is very little data coming from the region so this is largely conjecture. The layer of buried surface hoar is my biggest concern moving into the weekend. Where it exists it is probably reaching a burial depth of around 60cm. This depth was associated with several skier and remotely triggered avalanches in the deeper snowpack around Terrace last weekend.

Snowpack Summary

By my reckoning up to 30cm of new snow has fallen in the last week. This means that as much as 60cms of settled snow may now sit on a layer of buried surface hoar. I'm unsure about how widespread this layer is; I suspect that it is most likely to be found lurking on sheltered north facing slopes at tree-line and just below, although it is possible that in some areas it may extend into the alpine. Easterly winds have reverse loaded lee feature.  Lower below tree-line elevations may still be below the threshold for avalanches.

Avalanche Problems

Persistent Slabs

The new snow may sitting on a buried layer of surface hoar. Where it exists, I suspect that it is buried close to a critical depth for human triggered avalanches.
Avoid open slopes and convex rolls around tree-line where buried surface hoar may be preserved.>Dig down to find and test weak layers before committing to a slope. Share your observations on the Mountain Information Network.>

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 4

Wind Slabs

Moderate winds from the east on Thursday have reverse loaded lee features.
Use caution when traveling in areas that have been reverse loaded by winds.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3