Avalanche Forecast

Issued: Jan 22nd, 2021 4:00PM

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

Avalanche Canada cgarritty, Avalanche Canada

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Adopt a cautious mindset of initial assessment if you're among the first travelers in White Pass when the road opens. Be aware of the overall weaker snowpack structure found in thinner snowpack areas of the region if the closure has you considering alternate objectives.

Summary

Confidence

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

Weather Forecast

FRIDAY NIGHT: Increasing cloud. Light west winds.

SATURDAY: Cloudy with isolated flurries and a trace of new snow, increasing a bit overnight. Light southwest winds, increasing overnight. Alpine high temperatures around -9.

SUNDAY: Cloudy with lingering isolated flurries and about 5 cm of new snow from overnight. Light southwest winds. Alpine high temperatures around -10

MONDAY: Mainly cloudy. Light to moderate southwest winds. Alpine high temperatures around -13.

Avalanche Summary

A widespread natural avalanche cycle occurred during the height of the recent storm with naturally triggered storm slabs reported up to size 3. 

Recent observations from the White Pass area are lacking due to the road closure, however explosives control on Thursday in the pass south of the US border produced consistent slab releases to size 2. This gives some indication of hazards that may exist on the Canadian side once the road opens.

We got some good MIN posts last weekend from the Wheaton Valley where one group found some older avalanche activity and another where skiers found some shooting cracks in the new snow.

Our field team took a quick look around last Saturday while the road was closed. They found evidence of a natural avalanche cycle to size 1.5 with crowns up to 30 cm in depth. Interestingly, this kind of activity was found in upper treeline and alpine terrain. More details here.

Snowpack Summary

40-60 cm recent snow and strong southwest, shifting to northerly winds have created widespread and reactive wind slabs on a variety of aspects. The recent snow and wind have also created large and fragile new cornice growth.

Around Log Cabin, around 70 cm of snow may overlie a layer of surface hoar. This layer was the culprit of avalanche activity during the first week of January. This layer has not been reported elsewhere in the region.

A buried crust from early December can be found 50-130 cm below the surface, but most reports suggest the snow is well-bonded to it.

The lower snowpack is strong around White Pass, but there is potential for a generally thinner and weaker snowpack structure to exist in inland areas, such as the Wheaton Valley and even more so in the south Klondike.

Terrain and Travel

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Avoid lee and cross-loaded terrain.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Watch for areas of hard wind slab on alpine features.

Problems

Wind Slabs

An icon showing Wind Slabs

40-60 cm of storm snow and strong southwest, shifting to northerly winds have created widespread wind slabs on a variety of aspects. Expect these to remain reactive to the weight of a person or machine over the near term

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 23rd, 2021 4:00PM

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