Avalanche Forecast

Issued: Dec 21st, 2016 5:16PM

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

jfloyer, Avalanche Canada

Cariboos.

Mostly a storm and wind slab problem, but as the upper snowpack settles, things might start to change. If you see signs of instability, like whumpfs (rapid settlements), or see small rolls peel off, avoid unsupported (convex) terrain features.

Summary

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

Thursday: 5-10 cm new snow is expected. Ridgetop winds southwesterly 60-70 km/h in the morning, diminishing to westerly 40 km/h by the afternoon. Treeline temperatures around -3C. Friday: Light snow in isolated areas, no significant accumulation expected. Winds becoming light northwesterly. Treeline temperatures around -7C. Saturday: Dry and sunny. Light northeasterly winds. Treeline temperatures around -13C.

Avalanche Summary

No new avalanche activity was reported on Tuesday. I suspect a natural avalanche cycle occurred, however; the stormy conditions may have prevented people from getting out, or even being able to see alpine areas and/ or start zones. Forecast ridgetop winds are 60-90 km/hr and steady though Wednesday which will likely initiate another natural avalanche cycle.

Snowpack Summary

50-70 cm of new storm snow sits above a plethora of old snow surfaces including stiff wind affected snow, faceted (sugary) crystals and surface hoar crystals that formed in locations sheltered from the wind. The new storm snow was expected to bond poorly to these old surfaces; however, less avalanche activity than expected has been noted on this layer, indicating the bond may not be quite as poor as expected. The upper snowpack is still soft - as this becomes stiffer and denser, we may start to see more slab avalanche activity on this layer. The mid-November crust is now buried down 70-150 cm and produces variable results in snowpack tests.

Problems

Wind Slabs

Upper level winds have been very strong. Hard wind slabs have formed behind many terrain features in exposed areas.

Be aware of the potential for wide propagations due to the presence of hard windslabs.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Use caution in lee areas. Recent wind loading have created wind slabs.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Storm Slabs

Heavy storm snow amounts and strong southwest winds have built fresh and reactive storm slabs that sit over a variety of weak sliding layers. Rider triggering is likely.

Avoid all avalanche terrain during periods of heavy loading from new snow and wind.Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Dec 22nd, 2016 2:00PM