Avalanche Forecast

Issued: Dec 20th, 2017 4:25PM

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

Avalanche Canada mbender, Avalanche Canada

Choose conservative terrain in the coming days due to the presence of a persistent slab problem.

Summary

Confidence

Moderate - The weather pattern is stable

Weather Forecast

THURSDAY: Cloudy with flurries / wind light to moderate northwest / alpine temperature –13 FRIDAY: Mix of sun and cloud / wind moderate to strong north / alpine temperature -14 SATURDAY: Mainly sunny / wind moderate northwest / alpine temperature -11

Avalanche Summary

Reports from the past few days include several natural storm and wind slab avalanches to size 2.5 in the alpine and tree line. There have also been a few reports of skier accidental and remote (triggered from a distance) avalanches to size 1.5 and 2 at and below tree line. These avalanches are failing at the interface between the recent storm snow and the old snow surface. As snow settles and consolidates in the coming days expect to see in human triggered avalanche activity continue even as the stormy period ends.

Snowpack Summary

30-50cm of new snow accumulating over the last week sits on a wide variety of old surfaces including large surface hoar (weak, feather-like crystals), hard crusts formed by sun or wind, and sugary facets. As the snow load builds and slab properties develop, it will be important to monitor how the new snow is bonding to the old surfaces. Most concerning would be areas that have seen previous surface hoar development, such as sheltered areas at and below tree line and sheltered northerly aspects in the alpine. Additionally, any steep solar aspects where the surface hoar may be sitting on sun crust should be considered areas where this weak layer may be very likely to trigger. A crust which was formed by rain in late November is a major feature in the snowpack and is down approximately 60-100cm at tree line elevations. Snowpack tests suggest the snow above is currently bonding well to it. Snowpack depth decreases rapidly below tree line. Look out for early season hazards such as rocks, stumps, and open creeks.

Problems

Wind Slabs

An icon showing Wind Slabs
Recent west and northwest winds switching to north and northeast have formed windslabs in the lee of terrain features on a variety of aspects.
Be cautious as you transition into wind affected terrain.Use ridges or ribs to avoid pockets of wind loaded snow.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
Expect persistent slabs to be become more reactive as recent new snow settles into a slab. Likely spots are sheltered open areas at and below tree line or sheltered northerly aspects in the alpine.
Use conservative route selection, choose moderate angled and supported terrain with low consequence.Watch for whumpfing, shooting cracks, or signs of recent natural avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Dec 21st, 2017 2:00PM

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