Avalanche Forecast

Issued: Dec 26th, 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.

jlammers, Avalanche Canada

Kootenay Boundary.

Don't be fooled by the Moderate danger ratings. Buried weak layers still exist and may surprise in isolated terrain with nasty consequences.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

Wednesday: 3-5cm of new snow / Moderate westerly winds / Alpine temperature of about -15Thursday: 3-5cm of new snow / Light southerly winds / Alpine temperature of about -8Friday: 5-15cm of new snow / Light southerly winds / Alpine temperature of about -7

Avalanche Summary

No new avalanches have been reported. As new snow accumulates over the next few days, storm slabs should be on your radar. More importantly, the December 15th interface will become deeper and the overlying slab will likely settle and gain cohesion increasing the likelihood and destructive potential of this buried persistent weak layer.

Snowpack Summary

Last week's storm snow has now settled into a 30-80 cm soft slab. This slab overlies the December 15th interface which consists of a melt-freeze crust on steep, solar, higher elevation slopes and well-developed surface hoar everywhere else which seems most pronounced in sheltered treeline terrain and below. The bond at this variable interface is of critical importance, especially in areas where the overlying slab is deep and well-consolidated.The late November crust is now buried 60-100 cm and has been producing hard, resistant results in recent snowpack tests. Beneath this crust the lower snowpack is strong and well-settled.

Problems

Persistent Slabs

A well-developed layer of surface hoar is buried up to 80cm below the surface. These slabs may be easily triggered on steep or convex slopes and in sheltered areas at and below treeline.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.Watch for stiff or hollow feeling snow, whumpfing, or shooting cracks.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Wind Slabs

Variable winds have created wind slabs on most aspects in the alpine and exposed treeline areas. Although these slabs have gained some strength, they have the potential for human triggering, and may step down to the December 15th layer.

Watch for whumpfing, stiff or hollow feeling snow, shooting cracks or recent avalanches.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 27th, 2017 2:00PM