Avalanche Forecast

Issued: Dec 18th, 2014 8:02AM

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

jfloyer, Avalanche Canada

Kootenay Boundary.

A small storm Friday might give some localized areas of concern, while a bigger storm for Sunday is likely to give more widespread avalanche concerns.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

Two storms: a little one on Friday then a bigger one with warming on Saturday night and into Sunday. Friday: expect around 5-10 cm new snow with freezing levels around 1400 m and moderate southerly winds. Saturday: a brief lull in the snow with maybe even the odd break in the clouds. Saturday night/Sunday: Expect 20-30 cm new snow, initially falling as snow, then around midday Sunday getting warm with freezing levels reaching around 2000 m. Strong southwest ridgetop winds.

Avalanche Summary

On Wednesday, explosive testing produced small (size 1.5) avalanches on S to SE aspects at 2200 m in steep rocky terrain that were suspected to step down to the early November crust.

Snowpack Summary

10-20 cm new snow has buried a prominent surface hoar layer above a thick rain crust that extends as high as 2100 m. High elevation north aspect slopes do not have the rain crust, but on these slopes, facets or buried surface hoar from earlier in the month may be lurking under dense storm slabs. Recent snowpack tests at 2050 m in a NW aspect in Kootenay Pass produced moderate sudden results down 35 cm under the late-November crust and down 79 cm on facets above the early-November crust. Meanwhile in the Southern Purcells, snowpack tests last weekend gave easy sudden planer results on well preserved surface hoar where it was found down 30 cm on high north aspects.

Problems

Loose Dry

New snow is likely to sluff readily above a crust on steep terrain.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Be very cautious with gully features.>On steep slopes, pull over periodically or cut into a new line to manage sluffing.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

Old facet/crust weaknesses may still be sensitive to triggers on slopes that aren't bridged by a thick near-surface crust. Generally shady aspects in the high alpine.

Caution around convexities or areas with a thin or variable snowpack.>Be aware of thin areas that may propogate to deeper instabilites.>

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

Elevations: Alpine.

Likelihood

Unlikely

Expected Size

2 - 4

Valid until: Dec 19th, 2014 2:00PM