Avalanche Forecast

Issued: Jan 12th, 2018 3:55PM

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

Avalanche Canada mconlan, Avalanche Canada

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.

Summary

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.

Problems

Storm Slabs

An icon showing 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

An icon showing 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

Valid until: Jan 13th, 2018 2:00PM

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