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Avalanche Forecast

Archived

Mar 29th, 2025–Mar 30th, 2025

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

Regions

Kitimat, Nass, Rupert, Seven Sisters, Shames, Howson.

Cold snow exists on high northerly slopes but this is also where persistent weak layers are most likely to be triggered.

Use low-angle terrain and avoid overhead hazard to avoid this problem.

Confidence

Moderate

Avalanche Summary

Where a thick, supportive surface crust is found, we expect that triggering avalanches on buried weak layers is unlikely.

A natural avalanche cycle occurred last weekend, with very large slab avalanches (to size 4) failing on buried persistent weak layers. On Sunday, skiers remotely triggered a size 3 persistent slab near Shames (see photo). Reports of large avalanches to size 3 continued Tuesday through Thursday, likely triggered by warm temperatures or solar input.

Snowpack Summary

A melt-freeze crust has formed on most surfaces. Dry snow persists on northerly aspects at upper elevations.

Three persistent weak layers remain notable in the snowpack and have been responsible for recent large avalanches. Surface hoar that formed in mid-March can be found 50 to 100 cm below the snow surface. Below this, another layer of surface hoar that formed in early March can be found at a depth of 100 to 150 cm. Additionally, a layer of facets, surface hoar, and/or a crust from mid-February is buried 100 to 200 cm deep.

Weather Summary

Saturday Night

Partly cloudy. 30 km/h south ridgetop wind. Treeline temperature -9 °C.

Sunday

Partly cloudy. 30 km/h southeast ridgetop wind. Treeline temperature 0 °C. Freezing level rises to 1500 m.

Monday

Mostly sunny. 20 to 30 km/h south ridgetop wind. Treeline temperature 0 °C. Freezing level 1500 m.

Tuesday

Increasing cloud with a few flurries. 20 to 40 km/h southwest ridgetop wind. Treeline temperature -2 °C. Freezing level drops to 1000 m.

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.
  • Make conservative terrain choices and avoid overhead hazard.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.