Avalanche Forecast

Issued: Jan 26th, 2018 4:47PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. 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 - Due to the number of field observations

Weather Forecast

Saturday: Light snow. Light to moderate south-easterly winds. Alpine temperature near -10. Sunday: 5-10 cm snow. Moderate south-westerly winds. Alpine temperature near -7.Monday: 5-10 cm snow. Moderate south-westerly winds. Alpine temperature near -4.More information can be found in the Mountain Weather Forecast.

Avalanche Summary

Avalanche activity slowed on Thursday and Friday, but a few size 2.5-3 naturally and explosive-triggered slabs have been reported. These were around 120 cm deep and are suspected to have failed on the early January persistent weak layer. On Monday, there was evidence of a widespread natural avalanche cycle with very large avalanches being released (up to size 3.5). This occurred on all aspects, at all elevations, with depths of 40 to 100 cm, and generally occurring on the mid-January weak layer but sometimes on the mid-December layer. Also, a large (size 2.5) persistent slab avalanche was triggered by a skier at treeline, which stepped down to the mid-December weak layer. The slab was 65 cm deep and slid on a 30 to 35 degree north-facing slope.Although natural avalanche activity has diminished, there's still a good chance of triggering a surprisingly large avalanche with the weight of a person.

Snowpack Summary

The current snowpack is complex, with three active weak layers that professionals are monitoring. Recent storm snow has been shifted by winds to form wind slabs and cornices.Down about 30-70 cm is a crust and/or surface hoar layer buried mid-January. The crust is reportedly widespread, with the possible exception of high elevation north aspects. The surface hoar is up to 10 mm is size and has been reported at all elevation bands.Deeper in the snowpack, the early-January persistent weak layer is found 40 to 120 cm below the surface. It is composed of surface hoar on sheltered slopes and sun crust on steep solar aspects and found at all elevation bands. Snowpack tests show sudden fracture characters with easy to moderate loads and high propagation potential, as well as whumpfs and cracking with skier traffic. Another weak layer buried mid-December consisting of a facet/surface hoar/crust combination is buried 40 to 100 cm deep. It is most problematic at and below tree line.A rain crust buried in November is 100 to 150 cm deep and is likely dormant for the time being.

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.
Use caution in lee areas. Recent wind loading have created wind slabs.Use conservative route selection. Choose moderate angled and supported terrain with low consequence.Choose regroup spots that are out of avalanche terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

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.
Avoid steep convexities or areas with a thin or variable snowpack.Make conservative terrain choices, remembering that avalanches may be surprisingly large.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 3.5

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