Avalanche Forecast

Issued: Dec 25th, 2017 4:05PM

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

cgarritty, Avalanche Canada

Cariboos.

Keep seeking out soft, unconsolidated snow. Slab formation remains the critical factor for avalanche danger under present conditions. Plan on more conservative terrain selection at mid-elevations.

Summary

Confidence

High -

Weather Forecast

Tuesday: Mainly cloudy with isolated flurries bringing a trace of new snow. Light southwest winds. Alpine temperatures around -15.Wednesday: Cloudy with isolated flurries and a trace to 3 cm of new snow. Light southwest winds. Alpine temperatures around -17.Thursday: Mainly cloudy with isolated flurries and a trace to 3 cm of new snow. Light northwest winds. Alpine temperatures around -20.

Avalanche Summary

No new avalanches have been reported in the region. In addition to lingering wind slabs at higher elevations, persistent slab avalanche danger can be expected to persist in areas where the last week's storm snow consolidates into a slab above the December 15 interface. Please submit your observations to the Mountain Information Network (MIN).

Snowpack Summary

Last week's stormy weather brought 20-40cm of new snow to the region. Shifting winds (most recently from the northwest) have redistributed this storm snow into wind slabs on a variety of aspects at higher elevations while cold temperatures have inhibited slab formation in wind-sheltered areas. The storm snow lies over a variety of old surfaces, including large surface hoar (weak, feather-like crystals), crusts formed by sun or wind, and sugary facets. The bond at this old snow interface is of critical importance in areas where the overlying snow has consolidated into a slab. The most concerning areas areas are those that saw pronounced surface hoar development in advance of the storm, such as sheltered areas at and below tree line.A crust which was formed by rain in late November is another major feature in the snowpack and is down approximately 70-100cm at tree line elevations. Recent observations show this crust gradually breaking down, making it a less well-defined failure plane for avalanching.

Problems

Persistent Slabs

A weak layer of surface hoar buried 20-40 cm deep has potential to produce large avalanches where the overlying snow has settled into a cohesive slab. The greatest caution is needed around steeper, sheltered slopes at treeline and below.

Watch for signs of slab formation at lower elevations, such as whumphing or shooting cracks.Buried surface hoar is more likely to be preserved in sheltered openings at and below tree line.Surface hoar distribution is highly variable. Avoid generalizing your observations.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Wind Slabs

Shifting winds have redistributed last week's storm snow into wind slabs on a variety of aspects. Northwest winds were the most recent. Exercise extra caution at lower elevations where winds may have formed a slab over a touchy surface hoar layer.

Use ridges or ribs to avoid pockets of wind loaded snow.Be aware of recent variable wind loading patterns.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 26th, 2017 2:00PM