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Avalanche Forecast

Archived

Jan 17th, 2025–Jan 18th, 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 possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

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

The persistent slab is alive and well producing very large avalanches over the past few days.

Natural avalanches may taper but human triggering is likely.

Confidence

Moderate

Avalanche Summary

On Thursday, natural avalanche activity continued up to size 2 with a persistent slab size 3.5 reported.

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 wind- 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

Friday Night

Partly cloudy. 10 to 20 km/h north ridgetop wind. Treeline temperature -8 °C.

Saturday

Mix of sun and cloud. 10 to 25 km/h northwest ridgetop wind. Treeline temperature -10 °C.

Sunday

Cloudy with sunny periods. 10 to 20 km/h northeast ridgetop wind. Treeline temperature -8 °C. Freezing level valley bottom. Strong alpine above freezing layer.

Monday

Cloudy with some sunny periods and isolated flurries. 20 gusting to 45 km/h southwest ridgetop wind. Treeline temperature -5. Freezing level valley bottom.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Avoid freshly wind-loaded terrain features.
  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • Keep in mind that human triggering may persist as natural avalanches taper off.

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.

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.