Avalanche Forecast

Issued: Dec 25th, 2018 3:57PM

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

Avalanche Canada ghelgeson, Avalanche Canada

We're into a week of stable weather, but a persistent slab problem still warrants conservative terrain choices. Read more in the new forecaster blog here.

Summary

Confidence

Moderate -

Weather Forecast

The BC weather will take a holiday break over the next couple of days as the wild storm cycle of recent weeks eases in the Pacific.CHRISTMAS NIGHT: Freezing level at valley bottom, light variable wind, no significant precipitation expected. BOXING DAY: Broken cloud cover, freezing level at valley bottom, light southwest wind, trace of snow possible. THURSDAY: Broken cloud cover, freezing level at valley bottom, light northerly wind, no significant precipitation expected. FRIDAY: Scattered cloud cover, freezing level at valley bottom, light west/southwest wind with potential for moderate westerly gusts in the afternoon at upper elevation, trace of snow possible.

Avalanche Summary

Avalanche Control work on Monday produced avalanches from size 1 to 3 on north through northwest facing terrain between 1900 and 2700 m. One of the more interesting results was a size 1.5 wind slab that was remote triggered from 200 m away on a north facing slope around 2100 m. No new natural avalanche activity to report.On Sunday natural avalanche activity began to taper off, but large persistent slabs continued to be reactive to human and explosive triggers. On Sunday, a large (size 2.5) persistent slab avalanche was triggered by a snowmobiler in Silent Pass. The avalanche occurred on a wind loaded northwest-facing slope in the alpine. See details in the MIN report. Over the weekend explosives produced numerous large persistent slab avalanches (size 2-4) in alpine terrain. The avalanches occurred on all aspects and failed on several different weak layers including the early December weak layer and weak facets at the bottom of the snowpack. Over the past two weeks, several large persistent slab avalanches were remotely triggered from skiers on adjacent slopes, particularly in the Golden area.

Snowpack Summary

5-15 cm of low density snow sits above wind slabs in the alpine, and in some isolated areas above small surface hoar (feathery crystals).A weak layer that formed during the dry spell in early December is now 50-100 cm deep. The layer is composed of facets (sugary snow), surface hoar (feathery crystals), and a sun crust (on south aspects). Another similar weak layer is buried 80-150 cm. Finally, the base of the snowpack has weak faceted layers at alpine and treeline elevations. All of these weak layers have been producing large avalanches over the past week. Human triggering any of these layer is most likely on slopes that didn't previously avalanche and on slopes that have variable snowpack depth (such as rocky alpine features).

Problems

Persistent Slabs

An icon showing Persistent Slabs
The likelihood of persistent slab avalanches is gradually decreasing, but triggering one of the weak layers in the lower snowpack has major consequences. This problem will likely linger through the holidays.
Use conservative route selection, stick to moderate angled terrain with low consequence.Be wary of slopes that did not previously avalancheAvoid convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Wind Slabs

An icon showing Wind Slabs
Watch for wind slabs in lee and open terrain.
Use ridges or ribs to avoid pockets of wind loaded snow.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Dec 26th, 2018 2:00PM

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