Avalanche Forecast

Issued: Jan 26th, 2018 4:22PM

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

Avalanche Canada pgoddard, Avalanche Canada

Tricky conditions with a slowly increasing load over multiple weak layers in the snowpack. Take a conservative approach to your terrain choices.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Saturday: 5-15 cm snow. Moderate south-easterly winds. Alpine temperature near -10. Sunday: 5-10 cm snow. Moderate south-westerly winds. Alpine temperature near -7.Monday: 15-20 cm snow. Moderate to strong south-westerly winds. Alpine temperature near -2.More information can be found in the Mountain Weather Forecast.

Avalanche Summary

A widespread natural avalanche cycle was observed on Wednesday, with some natural activity continuing on Thursday. Avalanches up to size 4 were reported from all aspects and elevations, many failing on persistent weak layers down 1 m or more. The theme on Thursday was still a very touchy snowpack, with numerous avalanches triggered by snow cats, remote triggers, explosives, helicopters and people.Natural avalanche activity has now slowed, but the potential for human-triggering of surprisingly large avalanches remains elevated.

Snowpack Summary

70 to 100 cm of storm snow sits on a layer of crust and/or surface hoar from mid-January. The crust is widespread, with the possible exception of high elevation north aspects. The mid-January surface hoar is 5 to 20 mm in size and is likely present at all elevation bands. The recent storm snow fell with strong south winds, producing wind slabs in lee features at treeline and alpine elevations and in open areas below treeline.Deeper in the snowpack, the early-January persistent weak layer is buried 70 to 110 cm deep. It is composed of surface hoar on sheltered slopes and a sun crust on steep solar aspects and is present at all elevation bands. Recent snowpack tests have shown sudden fracture characters with moderate loads and high propagation potential, as well as other signs of instability such as whumpfs, cracking and avalanches. Yet another persistent weak layer buried mid-December is 100 to 150 cm deep and consists of a facet/surface hoar/crust combination. It is most problematic at and below tree line.A rain crust buried in November is 150 to 200 cm deep. While generally considered dormant, occasional activity has shown that it may react where it is less deeply buried.

Problems

Storm Slabs

An icon showing Storm Slabs
Recent snow and wind have built slabs that can be triggered by the weight of a person. A storm slab could step down to a deeper weak layer, creating a surprisingly large avalanche.
Be aware of the potential for wide propagations.Be very cautious as you transition into wind affected terrain, as wind slabs may be deep and touchy.If triggered storm/wind slabs may step down to deeper layers and result in very large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
Several weak layers are buried in the snowpack, creating very large avalanches when triggered.
Make conservative terrain choices, remembering avalanches may be surprisingly large.Avoid open slopes and convex rolls where buried surface hoar may be preserved.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Jan 27th, 2018 2:00PM