Avalanche Forecast

Issued: Dec 28th, 2017 4:59PM

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

Avalanche Canada ghelgeson, Avalanche Canada

Seek out conservative terrain Friday and be sure to have a safe exit route planned for the end of the day. Danger ratings could increase to high on Friday evening as the next storm system makes landfall.

Summary

Confidence

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

Weather Forecast

Most of BC finds itself under the influence of a massive arctic high-pressure system that has enveloped the province in an unseasonably cold, dry arctic air mass. In contrast, a milder, moisture-laden stream of air has taken aim at southwestern BC. These two air masses are set to clash over southern BC through Friday night, producing potentially heavy snowfall along the south coast before expected clearing begins on Saturday.THURSDAY NIGHT: Freezing level around 1200 m, moderate west wind, 10 to 30 cm of moist snow possible. FRIDAY: Overcast, freezing level around 1200 m, light southwest wind, 1 to 5 cm of snow possible. FRIDAY NIGHT: Freezing level beginning at about 1200 m, lowering through the night to valley bottom. 25 to 40 cm of snow possible. SATURDAY: Skies clearing throughout the day, freezing level at valley bottom, light NW wind, no snow expected.SUNDAY: Clear skies, freezing level at valley bottom, light variable wind, no snow expected.

Avalanche Summary

On Thursday skiers intentionally triggered avalanches on northwest trough southeast facing slopes to size 1.5. Crowns averaged 20 to 30 cm in depth and up to 90 m in width. Heavy snowfall and wind Thursday night through Friday night is expected to continue to drive a natural avalanche cycle.

Snowpack Summary

30 to 50 cm of storm snow has fallen as of Thursday afternoon. The new snow is reportedly upside down, meaning that wet heavy snow sits over light fluffy (lower density) snow. The storm snow covers a medley of old surfaces which include stubborn old wind slabs and wind scoured crusts in the alpine, and soft unconsolidated snow in sheltered areas at treeline and below.50 to 80 cm below the surface you'll likely find a couple of melt-freeze crusts which were buried mid-December. These layers may come to life as continued snowfall adds to the load. This would be most likely to occur in areas where loose facets exist above the crust.Below this, the snowpack is thought to be strong and well settled. The snowpack depth is about 150 cm at 1000 m, with many early season hazards present at lower elevations.

Problems

Storm Slabs

An icon showing Storm Slabs
Continued snow and strong wind Thursday night is expected to create fresh storm slabs that will likely remain sensitive to human triggers on Friday. These slabs will be most problematic in higher elevation lee terrain.
Continue to make conservative terrain choices while the storm snow settles and stabilizes.Avoid wind loaded features, especially near ridge crests and roll-overs.Avoid all avalanche terrain during periods of heavy loading from wind.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Dec 29th, 2017 2:00PM

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