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Avalanche Forecast

Archived

Jan 21st, 2025–Jan 22nd, 2025

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

Regions

Yukon, Tutshi, Wheaton, White Pass East, White Pass West.

Stick to conservative terrain free from overhead hazards. A reactive weak layer in the region is best managed by choosing simple terrain, and avoiding freshly wind-loaded slopes.

Confidence

Low

Avalanche Summary

On Tuesday, the field team observed two old size 2 wind slabs from the highway. We expect that natural wind slab avalanches likely occurred on Sunday and Monday during periods of strong wind.

Last Wednesday, a snowmobile remotely triggered a size 3 persistent slab from 100 m away near Bryant Lake. It was triggered from flat terrain at the col on an ENE aspect at 1500 m (MIN report).

Snowpack Summary

30-50 cm of settling storm snow from the last week can be found in sheltered terrain. Exposed terrain has been heavily wind-affected.

A weak layer of facets and a crust from early December is buried 50 to 100 cm deep. This layer exists on all aspects up to around 1700 m. This layer has shown recent reactivity, and we expect it to remain sensitive to human triggering.

Check out this recent ACMG Mountain Conditions Report for more on the persistent weak layer problem.

Weather Summary

Tuesday Night

Cloudy with light snowfall 2-4 cm. 30 to 50 km/h south ridgetop wind. Treeline temperature -6 °C.

Wednesday

Cloudy with 4-8 cm of snowfall. 40 to 60 km/h southwest ridgetop wind. Treeline temperature -5 °C.

Thursday

Partly cloudy with flurries. 30 to 50 km/h west ridgetop wind. Treeline temperature -4 °C.

Friday

A mix of sun and cloud. 30 to 50 km/h west ridgetop wind. Treeline temperature -3 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be aware of the potential for large avalanches due to buried weak layers.
  • Watch for newly formed and reactive wind slabs as you transition into wind-affected terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Remote triggering is a concern; avoid terrain where triggering overhead slopes is possible.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.