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Archived

Avalanche Forecast

Jan 12th, 2018–Jan 13th, 2018
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
3: Considerable
The avalanche danger rating below treeline will be considerable
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
3: Considerable
The avalanche danger rating below treeline will be considerable
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

Regions: Northwest Coastal.

New snow, strong winds, and a warming trend may create touchy storm slabs. These slabs could be sitting on wind slabs formed by the recent outflow winds. Conservative terrain choices are recommended.

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

FRIDAY NIGHT: Snowfall, accumulation 10-20 cm, moderate to strong southwesterly wind, alpine temperature near -10 C, freezing level below valley bottom.SATURDAY: Cloudy with light snowfall or freezing rain, accumulation 10 to 20 cm, moderate to strong southwesterly winds, alpine temperature rising to 2 C, inversion conditions with cold valley air and above-freezing level between about 1200 m and 2500 m.SUNDAY: Mostly cloudy with light precipitation in the morning, accumulation 5 mm, moderate to strong southerly winds, alpine temperature near 5 C, freezing level near 2500 m with inversion conditions.MONDAY: Mostly cloudy, moderate to strong southerly winds, alpine temperature near 4 C, freezing level near 2000 m with inversion conditions.

Avalanche Summary

Small naturally triggered wind slabs were observed on Thursday, along with other signs of instability such as cracking.  The slabs were observed on all aspects due to varying wind directions in the past few days.

Snowpack Summary

The snowpack is variable across the region. Wind slabs and storm slabs are found on some slopes in the alpine and at treeline.  Strong outflow winds have formed wind slabs on southerly and southwesterly lee features at all elevations.Up to 45 cm recent snow overlies several layers of interest in the upper snowpack. These include crusts, surface hoar and facets. A hard crust with associated facets from mid-December sits deeper in the snowpack, about 60 cm down. Any of these layers could create a persistent slab problem if new snow, wind-loading or warming change the properties of the slab above.The lower snowpack is generally strong, with the exception of areas around Stewart and further north where a basal crust and facets exist.

Avalanche Problems

Storm Slabs

New snow and strong winds will likely create touchy slabs at all elevations. The storm slabs may sit on wind slabs formed from strong outflow winds on Thursday and Friday.
Travel on ridgetops to avoid wind slabs on slopes below.Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 2

Persistent Slabs

A weak layer buried about 60 to 80 cm may become reactive with additional load and warming temperatures. Shallower slabs may step down to this layer and form large, destructive avalanches.
Avoid open slopes and convex rolls where buried weak layers may be preservedBack off if you encounter whumpfing, hollow sounds, or shooting cracks.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 3