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Avalanche Forecast

Archived

Jan 15th, 2025–Jan 16th, 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 possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Below Threshold.

Regions

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

Stick to simple terrain and avoid overhead slopes because the persistent slab avalanche problem is alive and well.It's possible to remote trigger very large avalanches from long distances

 

Confidence

Moderate

Avalanche Summary

On Wednesday, the Yukon team remotely triggered a large (size 3) persistent slab avalanche from 100 m away near Bryant Lake. It was triggered from flat terrain at the col on a ENE aspect at 1500 m. Crown depth is 100 to 200 cm, the width is 400 m and the length is 400 m. It ran on the December facet/ crust interface. Visibility on Wednesday showcased a natural avalanche cycle up to size 3 during the recent storm.

Human-triggered avalanches remain likely on Thursday.

Snowpack Summary

35 cm to 60 cm of storm snow continues to be redistributed by strong southwest winds building thick and reactive wind slabs on leeward slopes. A thin melt-freeze crust exists at lower elevations that saw rain.

A persistent weak layer consisting of a crust with 20 cm of faceted snow above it is buried 60 to 100 cm, and extends up to 1750 m. Snowpack testing has shown moderate results with a sudden collapse behaviour. This indicates that human triggering is possible.

Total snow depths are around 160–190 cm at treeline.

Weather Summary

Wednesday Night

Cloudy with clear periods and isolated flurries up to 5 cm. 15 to 40 km/h northwest ridgetop wind. Treeline temperature -12 °C.

Thursday

Mix of sun and cloud. 10 gusting to 40 km/h northeast ridgetop wind. Treeline temperature -12 °C.

Friday

A mix of sun and cloud. 20 km/h west ridgetop wind. Treeline temperature -15 °C.

Saturday

A mix of sun and cloud.10 to 25 km/h southwest ridgetop wind. Treeline temperature -15 °C. Possible above freezing layer.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Remote triggering is a concern; avoid terrain where triggering overhead slopes is possible.
  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • In times of uncertainty, conservative terrain choices are our best defense.

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.