Avalanche Forecast

Issued: Dec 23rd, 2017 4:41PM

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

Avalanche Canada cgarritty, Avalanche Canada

Slab formation remains the critical factor for avalanche danger under current conditions. The best and safest riding will be in soft, unconsolidated snow.

Summary

Confidence

Moderate -

Weather Forecast

Sunday: A mix of sun and cloud. Light west winds. Alpine temperatures around -15.Monday: Mainly cloudy. Light variable northerly winds. Alpine temperatures around -20.Tuesday: A mix of sun and cloud. LIght southwest winds. Alpine temperatures around -19.

Avalanche Summary

Reports from Friday included several ski cut Size 1 wind slabs on south aspects above 2100 metres in the north of the region. Reports from the previous few days showed a few size 1-1.5 remote triggered (triggered from a distance) avalanches in the alpine and at treeline.  Persistent slab avalanche danger can be expected to persist as our recent snow consolidates into a slab above the range of weak surfaces present at the December 15 interface. In areas where new snow has not yet consolidated into a slab, expect continued potential for triggering loose dry avalanches in steep terrain. Our persistent slab problem is expected to be touchier toward the south of the region where more snow accumulated during the recent storm.

Snowpack Summary

Last week's stormy weather brought 30-50cm of new snow top the region. The new snow lies over a wide variety of old surfaces, including large surface hoar (weak, feather-like crystals), hard crusts formed by sun or wind, and sugary facets. The bond at this old snow interface is critical where the overlying snow has consolidated into a slab. The most concerning areas areas will be those that have seen previous surface hoar development, such as sheltered areas at and below tree line and sheltered northerly aspects in the alpine. A crust which was formed by rain in late November remains 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
Shifting winds since the storm have been redistributing new snow into wind slabs on a variety of aspects, and another pulse of northwest wind may impact the north of the region over Saturday night. Watch for fresh slabs in lee terrain on Sunday.
Travel on ridges and/or ribs to avoid wind loaded slopes belowBe aware of areas that have been reverse loaded by winds

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
Reactivity at the buried December 15 interface will likely be greater where the new snow has settled into a cohesive slab above buried surface hoar. Use extra caution in wind affected areas and around steeper, sheltered slopes at treeline and below.
Be aware of increased danger in areas that received greater new snow accumulations.Buried surface hoar is more likely to be preserved in sheltered openings at and below tree line.Watch for signs of slab formation such as whumpfing, or cracking.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 24th, 2017 2:00PM