Avalanche Forecast

Issued: Jan 1st, 2018 4:59PM

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

jfloyer, Avalanche Canada

North Columbia.

Rapid warming is expected in the alpine, while persistent slab problems exist at treeline and below. Safe travel requires careful route selection. Steep, open or sparsely treed slopes are best avoided at this time.

Summary

Confidence

High -

Weather Forecast

Tuesday: Cold air in the valleys, warmer air up high. An above freezing layer is expected from approximately 2000-2500 m. Some valley cloud is possible, clear at upper elevations. Light westerly winds.Wednesday: basically a repeat of Tuesday, possibly slightly warmer.Thursday: Cloud developing. Lower elevations are finally expected to start to warm, although the above freezing layer is expected to remain in place. Light 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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

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. Especially at treeline, a small initial slide could step down to the persistent weak layer below.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 2nd, 2018 2:00PM