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Avalanche Forecast

Jan 3rd, 2019–Jan 4th, 2019
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
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Northwest Coastal.

More snow is forecasted for the southern part of the region. All of the recent snow will need time to strengthen.

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

THURSDAY NIGHT: Mostly cloudy with light snowfall in the south of the region, accumulation 10 to 15 cm in the south of the region, light to moderate southwest winds, alpine temperature -5 C, freezing level below valley bottom.FRIDAY: Cloudy with light snowfall, accumulation 5 cm in the south of the region, light to moderate southwest winds, alpine temperature -5 C, freezing level below valley bottom.SATURDAY: Cloudy with light snowfall, accumulation 5 to 10 cm, light to moderate southwest winds, alpine temperature -6 C, freezing level below valley bottom.SUNDAY: Mostly cloudy, light northwest winds, alpine temperature -7 C, freezing level below valley bottom.

Avalanche Summary

Reports indicate that a natural avalanche cycle occurred during the storm from Monday to Wednesday, with many large to very large avalanches (size 2 to 3.5) propagating widely and running far. For example, see the MIN reports here and here. Some of the avalanches, particularly in the north of the region, stepped down to the deeper weak layers described in the snowpack summary.

Snowpack Summary

The snowpack varies substantially with elevation. Above around 1400 m, expect to find upwards of 100 cm of recent storm snow, which fell with strong southwest winds. The deepest amounts will be in lee terrain features adjacent to ridges. Below around 1400 m, the storm began with snow and switched to rain and may have switched back to snow again around treeline and upper below treeline elevations. With colder air temperatures, expect any wet snow to freeze and form a melt-freeze crust. New snow Thursday night will fall on these surface.In the northern part of the region, all this snow may overly a couple weak layers of feathery surface hoar buried near the end of December. Expect to find these layers about 50 to 120 cm deep.For most of the region around 150 to 200 cm deep, a weak layer of sugary faceted snow buried on December 8 may still exist. It is likely that this layer was the culprit of a large, remotely-triggered avalanche on December 30 near Terrace, described in a MIN report here. Other reports indicate that this layer is still present and it could be triggered by humans in shallow snowpack areas. Storm slabs could step down to this layer and produce very large avalanches.

Avalanche Problems

Storm Slabs

Between 50 and 100 cm of snow fell with the recent storm at high elevations, with strong southwest wind. Around treeline and below, new snow will fall on a crust. The snowpack may be touchy to human activity on Friday.
Choose low-angle terrain without overhead exposure.Look for signs of instability such as whumpfs, hollow sounds, shooting cracks, or recent avalanches.Use caution in lee areas. Recent wind loading have created wind slabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1.5 - 3.5