Avalanche Forecast

Issued: Dec 24th, 2018 3:44PM

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 shorton, 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

MONDAY NIGHT: Cloudy with clear periods, light wind, alpine temperature drop to -12 C.TUESDAY: Mix of sun and cloud, light wind from the west, alpine high temperatures around -10 C.WEDNESDAY: Mix of sun and cloud, light wind from the west, alpine high temperatures around -12 C.THURSDAY: Mix of sun and cloud, light wind from the northwest, alpine high temperatures around -12 C.

Avalanche Summary

Natural avalanche activity has started to taper off, but large persistent slabs continue to be reactive to human and explosive triggers. On Sunday, a large (size 2.5) persistent slab avalanche was triggered by a snowmobiler in Singing Pass. The avalanche occurred on a wind loaded northwest-facing slope in the alpine. See details in the MIN report. Over the weekend explosive in 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 facets 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.
Avoid convexities or areas with a thin or variable snowpack.Be wary of slopes that did not previously avalancheUse conservative route selection, stick to moderate angled terrain with low consequence.

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.
If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Use ridges or ribs to avoid pockets of wind loaded snow.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Dec 25th, 2018 2:00PM