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Avalanche Forecast

Archived

Jan 20th, 2021–Jan 22nd, 2021

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Below Threshold.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Below Threshold.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Below Threshold.

Regions

Yukon.

  

Recent snow and strong southwest, shifting to northerly winds have created reactive wind slabs on a variety of aspects. Use caution when transitioning into wind affected terrain.

Confidence

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

Weather Forecast

  

WEDNESDAY NIGHT: Partly cloudy / Light, west ridgetop wind / alpine low temperature -12 / Freezing level valley bottom.

THURSDAY: Mostly cloudy with sunny periods / Light, northwest ridgetop wind / alpine high temperature -10 / Freezing level valley bottom.

FRIDAY: Mix of sun and cloud / Moderate, west ridgetop wind / alpine high temperature -13 / Freezing level valley bottom.

SATURDAY: Mostly cloudy / Light, south ridgetop wind / alpine high temperature -11 / Freezing level valley bottom.

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.

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 cornices.

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 week of Monday, January 4th. 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. 

Terrain and Travel

  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Watch for areas of hard wind slab on alpine features.
  • Avoid lee and cross-loaded terrain.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.