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Avalanche Forecast

Archived

Feb 19th, 2024–Feb 20th, 2024

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

Tricky Moderate. Some wind slabs have stabilized, others sit on triggerable weak layers. Some sheltered snow lacks slab properties, some has just enough to produce a surprising avalanche.

Confidence

Moderate

Avalanche Summary

Several natural, rider and explosive-triggered avalanches occurred last week. Notably, a large avalanche triggered by skiers occurred on Saturday. Check this MIN for details.All the recent avalanches were either wind slabs or persistent slabs failing on the weak layers described in the snowpack summary.

The chance of rider-triggered avalanches is expected to persist through this 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

Monday night

Cloudy with isolated flurries. 5 - 10 km/h north alpine wind. Freezing level to valley bottom.

Tuesday

A mix of sun and cloud. 5 - 15 km/h north alpine wind. Treeline temperature -2 °C with freezing level to 1000 m. Possible above freezing layer around 1500 m.

Wednesday

Mainly sunny. 10 - 15 km/h variable alpine wind, easing and shifting west. Treeline temperature -2 °C with freezing level to 900 m. Possible above freezing layer around 1500 m.

Thursday

Mainly sunny. 20 - 30 km/h southwest alpine wind, increasing. Treeline temperature around 0 °C with freezing levels rising to 1400 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • 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.