Avalanche Forecast

Issued: Jan 5th, 2018 6:36PM

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

Avalanche Canada ghelgeson, Avalanche Canada

A slab up to 100 cm in depth is consolidating above a volatile weak layer which has recently produced large avalanches. At and below treeline you need to carefully travel with intention to avoid convexities, steep features and rocky outcroppings.

Summary

Confidence

High -

Weather Forecast

A couple of weak residual lows will bring patchy light precipitation to the Kootenay Boundary through the weekend.FRIDAY NIGHT: Freezing level around 600 m, light to moderate southwest wind, 2 to 10 cm of snow expected.SATURDAY: Overcast, freezing level around 900 m, light west wind, 1 to 5 cm of snow.SUNDAY: Overcast, freezing level around 900 m, light south wind, 1 to 5 cm of snow.MONDAY: Overcast, freezing level around 1000 m, light south wind, trace of snow possible.

Avalanche Summary

On Thursday a skier triggered a size 3 avalanche just after entering the east face of Evening Ridge near Nelson. The avalanche released to ground and the late November crust was likely involved. The avalanche caught and carried the skier for over 300 m, resulting in significant injuries.  Also on Monday, loose wet natural avalanches were observed on solar aspects between 1150 and 1500 m. A natural size 1.5 persistent slab avalanche likely failing on the mid-December surface hoar was observed on a west facing feature during the heat of the day.On Monday another avalanche failing on the mid-December interface was triggered remotely from 10 m away as a skier approached a rocky outcropping on an east/southeast facing feature around 1900 m, MIN report with photos here. A skier also triggered a small storm slab on a west facing feature around 2200 m Monday which was suspected to have failed on the late December surface hoar. On New Years Eve a skier was involved in an avalanche on an east facing treeline feature at Kootenay Pass. A recent crown profile has shown that this avalanche failed on the late November crust/facet interface.

Snowpack Summary

Storms last week produced 25 to 50 cm of low density snow that was accompanied by moderate to strong winds generally out of the south. This snow rests on the late December surface hoar in sheltered locations. Warming alpine temperatures this week began to moisten the snow surface on steep southerly aspects and surface hoar once again covers the present surface in many locations.Between 50 and 100 cm below the surface you'll find the December 15th interface which is comprised of well-developed surface hoar that is most pronounced at treeline, but it is present below treeline too. The overlying slab is now deep and is gaining cohesion with time and continued warm temperatures as evidenced by recent avalanche activity listed above.Two laminated crusts created by twin rain events in late November lay just below the December 15th interface, 70 to 110 cm below the surface. Facets may be found sandwiched between the two crusts and have been observed above the uppermost crust too. In shallow rocky terrain the mid December Surface Hoar and the late November crust seem to be reacting together which is a volatile combination.

Problems

Persistent Slabs

An icon showing Persistent Slabs
Surface hoar is now buried up to 100 cm deep and has recently produced large human triggered avalanches. This slab appears to be most sensitive at treeline, but it is present below treeline too.
Avoid convexities, steep features and slopes with rocky outcroppings.It's critical to stay disciplined and choose only well supported, low consequence lines.The trees are not a safe haven right now.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Loose Dry

An icon showing Loose Dry
New snow Friday night and Saturday is expected to come in with very little wind and land on surface hoar and/or a crust. While it's unlikely for storm slabs to develop, small loose dry "sluff" avalanches are possible.
Be cautious of sluffing.Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.The recent snow may be hiding stubborn old wind slabs, especially near ridgecrest.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 6th, 2018 2:00PM