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Avalanche Forecast

Archived

Feb 20th, 2024–Feb 21st, 2024

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

Regions

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

Normal cautions should be sufficient to manage lingering wind slab and isolated persistent slab issues. It's not quite open season out there.

Confidence

Moderate

Avalanche Summary

Small rider-triggered wind slabs have continued to figure in reports from the early week, with one new report of a slab failing on the buried surface hoar/facets from early February. This occurred well south of the region but in similar snowpack conditions.

Small, natural wet loose avalanches were also prominent in Monday's reports.

Significantly more natural, rider and explosive-triggered wind slabs and persistent slabs on the same layer were reported last week.

Snowpack Summary

All exposed terrain at treeline and above is highly wind affected by recent strong winds from variable directions.

In sheltered terrain, a new layer of surface hoar is forming on the surface. A sun crust may be found on steep south and west-facing slopes.

An older layer of surface hoar and/or facets may be found buried 20 - 40 cm in sheltered terrain. It is most problematic where wind has added to this depth and contributed to slab formation above the layer.

A crust from late January can be found down 20-50 cm.

Weather Summary

Tuesday night

Mainly clear. 5 - 10 km/h north alpine wind. Freezing level to valley bottom.

Wednesday

Mainly sunny. 5 - 10 km/h northeast alpine wind, easing and shifting northwest. Treeline temperature -1 °C with freezing level to 1100 m. Possible above freezing layer around 1500 m.

Thursday

Mainly sunny with cloud increasing. 20 - 30 km/h southwest alpine wind, increasing. Treeline temperature around 0 °C with freezing levels rising to 1300 m.

Friday

Cloudy with flurries continuing from the overnight period bringing 5-15 total cm of new snow. 60 - 70 km/h southwest alpine winds. Treeline temperature -2 with freezing levels to 900 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Carefully evaluate steep lines for wind slabs.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

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.