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Avalanche Forecast

Archived

Jan 7th, 2025–Jan 8th, 2025

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

Regions

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

Storm slabs have been remain reactive to human-triggers.Conservative terrain choices and avoiding overhead hazard is strongly recommended

Confidence

Moderate

Avalanche Summary

The field team remotely triggered a large (size 2) storm slab that stepped down to the persistent weak layer on Tuesday by the Fraser Chutes. They also experienced signs of instability like whumpfing and shooting cracks in many steeper wind loaded pockets.

We expect the likelihood of both natural and human-triggered avalanches to remain elevated in White Pass during this stormy period.

Snowpack Summary

Up to 30 cm of new snow accompanied by strong southerly winds built storm slabs on Monday night. The majority of the snow fell in White Pass, with drastically less snow falling further inland. An additional 2 to 10 cm is expected by end of day Wednesday.

Due to the forecast winds, we expect the most reactive storm slabs will be on north-facing slopes.

An additional concern is a persistent weak layer of a crust with overlying facets, and in some cases surface hoar. This interface is currently buried 20 to 30 cm deep and extends up to 1750 m.

Despite the presence of faceted grains in the lower snowpack, there are no current layers of concern below the crust. 

Snowpack depths range from about 70 to 180 cm.

Weather Summary

Tuesday Night

Cloudy with 0 to 5 cm of new snow. 50 km/h southwest ridgetop wind. Treeline temperature -4 °C.

Wednesday

Cloudy with 0 to 6 cm of snow. 50 to 60 km/h southwest ridgetop wind. Treeline temperature -3 °C.

Thursday

Cloudy with 10 to 20 cm of snow. 60 to 70 km/h southeast ridgetop wind. Treeline temperature -3 °C.

Friday

Cloudy with 3 to 10 cm of snow. 60 km/h southwest ridgetop wind. Treeline temperature 0 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be careful as you transition into wind-affected terrain.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.