Avalanche Forecast

Issued: Feb 3rd, 2017 4:17PM

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

Avalanche Canada swerner, Avalanche Canada

New snow and wind will likely build reactive storm slabs. Storm slabs may have the potential to trigger deeper weakness in shallow snowpack areas. Conservative terrain selection is key for the weekend.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The weather pattern has finally shifted as a surface low moves onto the Interior bringing new snow through the weekend. Saturday: Snow amounts 10-20 cm with light- gusting strong southwest winds. Alpine temperatures near -4 and freezing levels 1200 m. Sunday: Snow amounts up to 20 cm with strong southwest winds. Alpine temperatures -3 and freezing levels 1300 m.Monday: Snow accumulations up to 20 cm with light southwest winds. Alpine temperatures near -3.

Avalanche Summary

No new avalanche observations were reported on Thursday. New building storm slabs will likely have a poor bond to the old snow surfaces and be reactive through the weekend, potentially stepping down and initiating deep persistent slabs.

Snowpack Summary

New snow has buried a variety of old snow surfaces including stiff wind slab or wind effected snow at upper elevations, sun crust on steep southerly slopes and surface hoar in sheltered areas. Below the surface, 50-65 cm of settled snow now sits above an interface that was buried in mid-January. The interface is composed of weak facets, surface hoar, and/or sun crusts and the strength of the bond is reportedly variable. Recent snowpack tests have shown sudden results on that interface. Areas with a shallower snowpack (less than 150 cm) have a generally weak snowpack structure with sugary facets near the ground. This includes shallow alpine slopes and most of the Rossland range. These deeper weaknesses warrant monitoring and create a complicating picture. It may be a low probability that you would trigger an avalanche that failed on these basal facets, however; the consequences could be detrimental. These layers may be unreactive but they could reawaken with more snow load.

Problems

Storm Slabs

An icon showing Storm Slabs
Reactive storm slabs will likely have a poor bond to the variety of old snow surfaces.
Avoid avalanche terrain during periods of heavy loading from new snow, wind.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Additional loading from new storm snow and wind may have enough mass to overload the weaker facets that exist mid-pack and/ or deeper in the snowpack. If reached critical load, the potential for full depth avalanches
If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Feb 4th, 2017 2:00PM