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Avalanche Forecast

Jan 13th, 2013–Jan 14th, 2013
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
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
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
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 Coastal.

Temperatures are forecast to rise significantly early this week. This rapid increase in temperature will result in a spike in avalanche danger. For advice on how to manage these changing conditions please refer to the latest forecaster's blog. 

Confidence

Fair

Weather Forecast

Monday: Low cloud with a chance of precipitation. An above freezing layer (AFL) is expected to develop between 1500 and 3000 m. Mountaintop temperatures could reach +5. Winds are moderate from the northwest. Tuesday: Light precipitation (possible freezing rain). The AFL remains between 1000 and 2000 m. Winds are moderate from the northwest. Wednesday: Cloudy with a chance of flurries. The AFL dissipates and the freezing level returns to 1000 m. Winds remain moderate from the northwest.

Avalanche Summary

There are a few reports of glide releases in steep south facing terrain. Explosive control work near highway corridors over the past couple days produced several avalanches up to size 3.5. Some of these slides released on the late December surface hoar or facet layer and propagated widely.

Snowpack Summary

The snow surface consists of wind slab, surface hoar, and weak facetted snow depending on aspect and elevation. Below this 60-90 cm of storm snow from last week continues to settle and gain strength. However, a weak layer of surface hoar or facetted snow sits at the base of the storm snow. Recent snowpack tests give generally moderate sudden planar, or "pops", results on this buried surface hoar layer and indicate potential for wide propagation. Near the base of the snowpack, a crust/facet layer continues to concern local avalanche professionals. This seems most prevalent near Bear Pass where the snowpack distribution is quite variable. 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.

Avalanche Problems

Persistent Slabs

A buried weak layer of surface hoar and/or facetted, down 70-90 cm, could wake up as temperatures rise rapidly early this week. Be particularly cautious on southerly aspects if the sun is also shining.
Avoid travelling on slopes which are becoming wet due to rain, warm temperatures, or sun.>Choose well supported terrain without convexities.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 5

Wind Slabs

Northerly outflow winds have created new wind slabs in exposed lee and cross-loaded terrain.
Be cautious as you transition into wind affected terrain.>Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 3