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Avalanche Forecast

Archived

Jan 3rd, 2023–Jan 4th, 2023

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

Triggering slab avalanches is possible on steep and convex slopes in treeline and alpine terrain.

Confidence

Moderate

Avalanche Summary

Recent avalanche activity has been relatively quiet, with primarily small (size 1) wind slabs and dry loose avalanches reported on Sunday and Monday. However, we continue to get periodic reports of large human-triggered persistent slab avalanches. Most recently, two size 2 persistent slabs were triggered on treeline features in the northern part of the region on Monday. These avalanches failed on 30 to 50 cm deep facet layers. Similar avalanches were reported in treeline terrain in southern parts of the region last Thursday and Friday. This ongoing activity suggests it is still possible to trigger persistent slabs in specific alpine and treeline terrain features.

Snowpack Summary

Shifting winds are redistributing 15 to 30 cm of recent snow leaving wind slabs on lee terrain features. Wind slabs are also likely found on cross-loaded features in coastal inlets due to outflow winds. Below 1000 m a crust exists on or near the surface.

40 to 70 cm overlies a weak layer that formed during the Arctic outbreak in mid-December. In the alpine this layer is generally facets, but some surface hoar has been reported. At treeline, it is more likely to find surface hoar at this interface in sheltered terrain.

A layer of surface hoar and facets from early December can be found down 70 to 100 cm. This layer has not been reactive recently, although still produces some sudden results in snowpack tests.

Weather Summary

Tuesday night

Cloudy with isolated flurries and trace accumulations of snow, 40 km/h wind from the southeast, treeline temperatures drop to -8 °C.

Wednesday

Partly cloudy in the morning with sunny periods in the afternoon, no precipitation, 20 km/h wind from the east, treeline temperatures around -4 °C.

Thursday

Mix of sun and cloud, no precipitation, 30 to 50 km/h wind from the southeast, treeline temperatures around -6 °C.

Friday

Cloudy with flurries increasing in intensity throughout the day, 5 to 10 cm of snow by the late afternoon, 40 to 60 km/h wind from the south, treeline temperatures warm to -3 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Caution around convexities or sharp changes in terrain.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.

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.