Avalanche Forecast

Issued: Jan 2nd, 2018 4:52PM

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

jfloyer, Avalanche Canada

North Columbia.

Warm alpine temperatures and a persistent weak layer 50-70 cm below the surface are both good reasons to be cautious.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

Wednesday: Cold air in the valleys, warmer air up high that is expected to get close to 0C above 2000m. Some valley cloud is possible, clear at upper elevations. Light variable winds.Thursday: Clear in the morning, cloud developing through the day. Inversion conditions expected to persist. Moderate southwesterly winds.Friday: Cloudy with light snow. Freezing level 500 m. Moderate southwesterly winds.

Avalanche Summary

There have been a several recent reports of remote-triggered (triggered from a distance) persistent slab avalanches to size 2 on west, south and northerly aspects between 1400-1800m. Reactivity on the persistent slab is likely to increase with warmer temperatures as the upper snow becomes denser.

Snowpack Summary

30-50cm of low density new snow from last week has buried a layer of weak feathery surface hoar and/or sugary facets. This new snow is expected to start to consolidate into a slab once forecast warmer temperatures take effect, but so far the upper snow has been remained light and soft. Of greater concern is a weak layer buried mid-December that consists of surface hoar, a sun crust and/or sugary facets, and is now down approximately 50-70cm.The bond at this interface is highly variable. The most concerning areas are those that saw pronounced surface hoar development before mid-December, such as sheltered areas at and below treeline, sheltered northerly aspects in the alpine, or anywhere the surface hoar formed on top of a sun crust. Recent snowpack tests show wide ranging reactivity on this weak layer but suggest that it may be most reactive on northerly aspects. A rain crust that formed in late November is now buried 80-120cm deep. Treeline snow depths are in the region of 200 cm.

Problems

Persistent Slabs

A weak layer of surface hoar buried 50-80 cm deep has potential to be reactive in areas where the overlying snow has settled into a cohesive slab.

Watch for signs of slab formation, such as whumpfing and shooting cracksApproach steep open slopes cautiously at and below treeline where buried surface hoar may exist.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Storm Slabs

With expected warm temperatures, recent storm snow will settle into a denser slab, making triggering avalanches in steep terrain more likely.

If triggered the storm slabs may step down to deeper layers resulting in large avalanches.Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 3rd, 2018 2:00PM