Avalanche Forecast

Issued: Dec 19th, 2017 4:45PM

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

Avalanche Canada mbender, Avalanche Canada

Expect the recent storm slab to become more reactive as it continues to settle and consolidate.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Wednesday

Weather Forecast

WEDNESDAY: Periods of snow in the southern portion of the region Tuesday into Wednesday, accumulations 5-10cm / wind light to moderate northwest / alpine temperatures -11 THURSDAY: Mainly cloudy with isolated flurries / wind moderate northwest / alpine temperature -9  FRIDAY: Mainly sunny / wind moderate north / alpine temperature -15

Avalanche Summary

Reports from the past 2 days include several explosives controlled and natural storm snow 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. This avalanche activity is failing in the recent storm snow. As snow accumulates and settles in the coming days expect to see in human triggered avalanche activity continue even as the latest forecast storm ends.

Snowpack Summary

30-50cm of new snow accumulating over the past 5 days 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 50-80cm 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 have created wind slabs in the lee of terrain features
Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Storm Slabs

An icon showing Storm Slabs
Expect the new snow to be become more reactive as it settles into a slab especially in sheltered areas at and below tree line where it may be sitting on a layer of feathery surface hoar crystals.
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

Likely

Expected Size

1 - 2

Valid until: Dec 20th, 2017 2:00PM

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