Avalanche Forecast

Archived

Feb 28th, 2025–Mar 1st, 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 possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

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

Natural avalanche activity may taper off, but the snowpack remains primed for human triggering.

Start with a very conservative trip plan and back off if you encounter signs of instability.

Confidence

Moderate

Avalanche Summary

On Thursday, several human triggered avalanches were reported up to (size 2). The most significant ones were remotely triggered from up to 200 m away.

The stormy conditions proved a widespread natural avalanche cycle up to size 3. Many of these avalanches have been reported as wind, storm and persistent slabs at upper elevations and wet loose at lower elevations.

Natural avalanches may taper, but the snowpack could remain primed for human triggering.

Snowpack Summary

Over the past few days, up to 50 cm of new storm snow accompanied by strong southerly wind hit the region. Wind-transported snow has likely built deeper slabs on northerly aspects at upper elevations. Lower elevation snow may be crusty as freezing levels fall.

The upper metre of the snowpack is complicated. This snow sits above several significant weak layers that formed during the January and February dry spells. These include facets, surface hoar (in sheltered terrain), and crust on solar aspects.

A layer of facets on top of a crust from early December is buried 100 to 200 cm deep. This layer is generally not a concern in this region.

Weather Summary

Friday Night

Cloudy with 5 to 10 cm of snow. 20 to 45 km/h south ridgetop wind. Treeline temperature -1 °C. Freezing level 1000 m.

Saturday

Cloudy with 5 to 10 cm of snow. 20 to 45 km/h south ridgetop wind. Treeline temperature -1 °C. Freezing level 900 m.

Sunday

A mix of sun and cloud. 20 to 30 km/h northwest ridgetop wind. Treeline temperatures -1. Freezing level 1000 m.

Monday

Sunny with few cloud. 10 to 20 km/h northeast ridgetop wind. Treeline temperatures -7. Freezing level 1000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Keep your guard up as storm slabs may remain sensitive to human triggering.
Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Keep in mind that human triggering may persist as natural avalanches taper off.
Stick to simple terrain or small features with limited consequence.

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.