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Avalanche Forecast

Archived

Feb 11th, 2023–Feb 12th, 2023

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

Regions

Northwest Coastal, Kitimat, Nass, Rupert, Seven Sisters, Shames, Stewart, Howson, Ningunsaw.

Avoid avalanche terrain. New touchy storm and wind slabs will form throughout the day.

Confidence

High

Avalanche Summary

On Thursday the fresh snow was reactive to skiers, with sluffing, natural storm slab avalanches to size 2.5, and wind slabs to size 1.5 reactive to skiers. With more snow in the forecast, expect the snowpack to continue to be reactive to skier- and rider-traffic.

On Wednesday, skiers triggered a large, size 2, avalanche near Ningunsaw. The Deep Persistent avalanche was triggered on an east aspect near ridgetop in a thin, rocky start zone and failed on basal facets.

Snowpack Summary

40-70 cm of recent storm snow overlies older wind-affected surfaces and a supportive melt-freeze crust up to 1800 m and steep solar slopes. South-southwesterly winds have been scouring and pressing southerly slopes and wind slabs on northerly aspects. Large cornices are also being reported on many northerly aspects.

80 to 200cm of storm snow from the past two weeks is settling over a layer of facets, crust, and previous wind-affected surfaces in alpine terrain. We're continuing to track this layer given recent avalanches on this interface under the patterns of continuous loading and successive natural avalanche cycles.

The mid and lower snowpack continues to bond and stabilize while a number of buried weak layers are still being tracked by professionals in the region, having produced a few large avalanches in the not-too-distant past.

Weather Summary

Saturday Night

Stormy with 5 to 30cm of new snow expected. Moderate to strong southwest winds and a low of -4 at 1500m.

Sunday

Stormy with 15 to 50cm of new snow expected. Strong southwest winds and a high of -3 at 1500m.

Monday

Cloudy with 5 to 15cm of new snow expected. Moderate westerly winds and temperatures at 1500m falling throughout the day to -8.

Tuesday

A mix of sun and cloud with the possibility of light flurries bringing trace amounts of new snow. Light southwest winds and a high of -10 at 1500m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid all avalanche terrain during periods of heavy snowfall.
  • Storm slab size and sensitivity to triggering will likely increase through the day.
  • Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
  • Avoid exposure to slopes that have cornices overhead.

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.