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Avalanche Forecast

Archived

Mar 13th, 2023–Mar 14th, 2023

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

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

New slabs are forming and they may sit on weak layers.

Confidence

Moderate

Avalanche Summary

Riders triggered a few small (size 1) wind slabs on Sunday, generally 10 to 40 cm deep on north to east aspects. Riders also noted loose dry sluffing running fast and far within the new snow.

Looking forward, the primary concern is new snow that overlies surface hoar and/or hard surfaces that formed last week. As the snow accumulates and forms slabs, they will likely become touchy to human traffic. There's uncertainty on when exactly this will happen so travelling conservatively and making observations as you travel will be key.

Snowpack Summary

Around 10 to 30 cm of snow has accumulated since Sunday. This snow overlies large (10 to 20 mm), weak surface hoar crystals in shaded wind-sheltered terrain, wind affected snow in wind-exposed terrain, and a hard melt-freeze crust on sun-exposed slopes. The wind was predominantly from the north to east on the weekend but it is switching to the southwest, meaning wind slabs may be found on all aspects.

Two more layers of surface hoar may be found about 40 cm and 80 cm deep. Weak faceted grains around a hard melt-freeze crust is found about 150 to 200 cm deep, though this layer is currently dormant.

The remainder of the snowpack is generally strong.

Weather Summary

Monday Night

Cloudy with snowfall, accumulation 2 to 5 cm, 20 km/h southwest wind, treeline temperature -10 °C.

Tuesday

Cloudy with snowfall, accumulation 2 to 5 cm, 30 km/h southeast wind, treeline temperature -9 °C.

Wednesday

Cloudy with snowfall then clearing, accumulation 5 to 15 cm, 30 to 50 km/h southwest wind, treeline temperature -7 °C, freezing level 600 m.

Thursday

Cloudy with snowfall, accumulation 5 to 10 cm, 30 to 40 km/h south wind, treeline temperature -5 °C, freezing level 1000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for fresh storm slabs building throughout the day.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.