Avalanche Canada ahanna, Avalanche Canada

Northwest Inland Avalanche Forecast

Jan 15th, 2020 4:00PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Wind Slabs.

It is dangerously cold and windy out there right now. Save your toes for more tolerable temperatures this weekend.

Summary

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

Wednesday night: Increasing cloud. Strong southeast outflows. Alpine temperatures around -34 C.

Thursday: Increasing cloud with isolated flurries bringing a trace of new snow. Strong east to southeast winds, decreasing to moderate over the day. Alpine temperatures around -32 C.

Friday: Mix of sun and cloud. Light south to southeast winds. Alpine temperatures around -26 C.

Saturday: Mix of sun and cloud with isolated flurries bringing 5-10 cm of new snow. Moderate southeast to southwest winds. Alpine temperatures around -20 C.

Avalanche Summary

On Wednesday, we received reports of skier triggered windslab avalanches size 1.5-2.5 around treeline. Crown depths were around 1 m, and they ran on a surface hoar layer buried by the recent storm on January 10th. 

Reports from the Bulkley Valley Monday detail natural windslab and persistent slab avalanche activity, size 2.5-3 on aspects lee to previous strong outflow winds. The persistent slab avalanches are suspected to be isolated incidents of avalanches running on the deep November crust.

Looking forward, windslabs are losing cohesion in the cold temperatures, but where they sit on surface hoar, the problem will likely remain well preserved.

Snowpack Summary

North to east aspects in the alpine have been wind scoured, with isolated hard windslab in lees. Wind effect also observed in open areas at treeline and below, where wind loaded pockets have been observed to exceed 1 m in depth, while snow in protected areas is unconsolidated and well preserved by the cold temperatures. 

Recent reports indicate that this wind affected surface snow overlies a layer of surface hoar in many areas, particularly at treeline. This layer has been associated with recent skier triggered avalanche activity. Deeper in the snowpack, another couple of surface hoar layers are currently buried about 80-120 cm below the surface in sheltered areas around treeline. There have been no reports of avalanche activity associated with them for a few weeks, during which several storm slab avalanche cycles have tested their potential for step-downs.

A deep crust from mid November lurks at the base of the snowpack. A couple of recent large avalanches are suspected to have run on this layer in isolated incidents high in the alpine.

Terrain and Travel

  • Watch for areas of hard wind slab on alpine features.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • The best and safest riding will be on slopes that have soft snow without any slab properties.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible

Expected Size

1 - 2.5

Previous strong outflow winds have blown snow into wind slabs extensively in the alpine and in open areas at treeline and below, where wind loaded pockets have been observed to exceed 1 m in depth. While windslabs may be losing cohesion in the cold temperatures, where they sit on surface hoar the problem will likely remain well preserved.

Aspects:

South East, South, South West, West, North West.

Elevations:

All elevations.

Valid until: Jan 16th, 2020 5:00PM