Avalanche Forecast

Issued: Dec 22nd, 2017 4:52PM

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

shorton, Avalanche Canada

South Rockies.

Conditions are highly variable. Wind slabs and a buried weak layer warrant a cautious approach to terrain. Read the forecasters' blog here for some great advice!

Summary

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

SATURDAY: Dry and sunny, strong northwest winds, temperatures around -17 C.SUNDAY: Dry and sunny with some clouds, moderate northwest winds, temperatures around -17 C.MONDAY: Mix of sun and cloud, light northwest winds, temperatures around -20 C.

Avalanche Summary

Over the past few days, avalanche activity has been reported in the east of the region where higher snow amounts occurred. This includes several large (size 2) explosive-triggered wind slabs on Friday. Smaller slabs have been triggered by skier traffic in steep terrain.

Snowpack Summary

In the southern and eastern parts of this region, up to 100 cm of snow has fallen in recent storms, combined with variable winds. In the Elk Valley, the amount of new snow is more like 40 cm. The new snow has fallen on a variety of surfaces including old crusts, wind-scoured surfaces and, in sheltered terrain at and below treeline, very large feathery surface hoar crystals. The two crusts that were buried near the end of November can be found lower in the snowpack. A third crust from the end of October exists near the base of the snowpack. Recent testing on this crust have not produced significant results.

Problems

Wind Slabs

Storm and wind slabs are sitting over a variable snow surface that may slide readily in some places (but not all). The snow needs time to bond!

Give the recent storm snow plenty of time to bond to underlying layers.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

A variable weak layer is buried 40-80 cm below the surface. It is most likely to be reactive in steep, unsupported terrain in sheltered locations where surface hoar crystals may have been preserved.

Watch for signs of instability such as whumpfing, or cracking. Choose well supported terrain without convexities.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Dec 23rd, 2017 2:00PM