Avalanche Forecast

Issued: Dec 21st, 2017 4:05PM

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.

jfloyer, Avalanche Canada

South Rockies.

While wind slab is likely the biggest concern, watch for a buried weak layer that could cause problems in steep terrain in sheltered locations.

Summary

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

Thursday night: 5-10 cm new snow expected.Friday: Flurries. Light easterly winds. Treeline temperatures around -12C.Saturday: Dry and sunny. Moderate northwesterly winds. Temperatures around -15C.Sunday: Dry and sunny. Light northwesterly winds. Temperatures around -15C.

Avalanche Summary

An avalanche cycle was reported from the east of the region on Wednesday where higher snow amounts occurred.

Snowpack Summary

In the southern and eastern parts of this region, up to a 80 cm of snow has fallen in recent storms, combined with variable winds. In the Elk Valley, the amount of new snow is more like 30 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 did not produce 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!

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

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

A variable weak layer is buried 30-60 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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Dec 22nd, 2017 2:00PM