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Avalanche Forecast

Archived

Jan 18th, 2025–Jan 19th, 2025

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

Regions

Northwest Coastal, Northwest Inland, Boundary, Stewart, Kispiox, Ningunsaw, Ningunsaw, Ningunsaw.

The persistent slab problem has produced very large avalanches recently.

Human triggering is likely, so don't let clear weather lure you into consequential terrain.

Confidence

Moderate

Avalanche Summary

On Friday, natural and rider-triggered avalanche activity continued up to size 2.5, with many persistent slabs failing on the early December weak layer between 50 and 150 cm deep.

Natural avalanche activity will likely taper over the weekend but the snowpack may be primed for human triggering.

Snowpack Summary

40 to 80 cm of storm snow fell across the region earlier in the week. Strong to extreme west through southwest wind created widespread wind-loading, with deeper deposits of snow found on leeward slopes. The winds are forecast to change directions which may start to load southerly aspects throughout the weekend.

At upper elevations down 30 to 60 cm a layer of surface hoar, facets, or a thin crust exists.

A persistent weak layer of surface hoar and facets overlying a crust is buried 100 to 200 cm deep. This layer was reactive during the storm, producing large and dangerous avalanches.

Weather Summary

Saturday Night

Clear. 10 to 20 km/h north ridgetop wind. Treeline temperature -15 °C.

Sunday

Mostly clear. 10 km/h northeast ridgetop wind, switching 20 km/h west ridgetop wind. Treeline temperature -15 °C.

Monday

Partly cloudy with trace snow. 30 gusting to 65 km/h southwest ridgetop wind. Treeline temperature -10.

Tuesday

Partly cloudy. 20 to 40 km/h west ridgetop wind. Treeline temperature -10 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Choose low-angled, sheltered terrain where new snow hasn't been wind-affected.
  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • Avoid freshly wind-loaded terrain features.
  • Keep in mind that human triggering may persist as natural avalanches taper off.
  • 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.