Avalanche Forecast

Issued: Dec 21st, 2017 3:59PM

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 - Due to the number of field observations

Weather Forecast

FRIDAY: Mix of sun and cloud / wind light  north / alpine temperature -14 SATURDAY: Mainly sunny / wind light to moderate northwest / alpine temperature -13 SUNDAY: Mix of sun and cloud / wind light to moderate northwest / alpine temperature -12

Avalanche Summary

Reports from the past few days include explosives controlled and natural storm snow avalanches to size 2.5 in the alpine and tree line. There have also been a several reports of skier accidental and skier remote (triggered from a distance) avalanches to size 1.5 at and below tree line. As the new 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

The 40-80cm of new snow accumulating over 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 90-120cm 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 east have formed windslabs in the lee of terrain features on a variety of aspects.
Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.Be aware of areas that have been reverse loaded by winds.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

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.
Watch for whumpfing, shooting cracks, or signs of recent natural avalanches.Buried surface hoar may be preserved on open slopes and convex rolls at and below tree lineUse conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Dec 22nd, 2017 2:00PM

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