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Avalanche Forecast

Archived

Jan 5th, 2023–Jan 6th, 2023

Alpine
Natural avalanches possible, human triggered probable.
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.

Intense wind is causing dangerous avalanche conditions in alpine terrain. Buried weak layers remain possible to trigger on steep and convex slopes.

Confidence

Moderate

Avalanche Summary

Minimal avalanche activity has been reported since Monday, with only a few small (size 1) wind slab avalanches observed when wind speeds increased on Wednesday.

Triggering large persistent slab avalanches remains a concern. The most recent report of a persistent slab avalanche was from Monday, when two size 2 persistent slabs were triggered on treeline features in northern parts of the region. 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 week (Dec 29 and 30).

Snowpack Summary

Strong to extreme wind is forming drifts and wind slabs in alpine terrain and along ridges. Recent storm snow continues to settle, with moist snow and crusts possibly forming on some surfaces. Several persistent weak layers may be found in the top metre of the snowpack, including a surface hoar layer buried on Dec 28 (30 to 50 cm deep) and a facet layer buried on Dec 23 (40 to 80 cm deep). These layers are increasing in strength, but could still be possible to trigger in specific areas. In alpine terrain, triggering one of these layers is most likely on steep rocky slopes where they present as facets, while in treeline terrain, they are most likely triggered on convex rolls in open trees where they present as preserved surface hoar.

Weather Summary

Thursday night

Cloudy with flurries starting at midnight and brining 10 cm around Kitimat, 5 cm around Terrace, and less farther north, 50 to 70 km/h wind from the southeast, treeline temperatures around -8 °C.

Friday

Stormy weather with 5 to 10 cm of snow, 60 to 80 km/h wind from the south, freezing level climbs to 700 m with treeline temperatures around -3 °C.

Saturday

Cloudy with afternoon flurries bringing 5 to 10 cm of snow, 40 to 60 km/h wind from the southeast, freezing level around 500 m with treeline temperatures around -3 °C.

Sunday

Mix of sun and cloud, no precipitation, 30 to 50 km/h wind from the east, treeline temperatures around -5 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Use conservative route selection and resist venturing out into complex terrain.
  • Be especially cautious as you transition into wind affected terrain.
  • Caution around convexities or sharp changes in terrain.

Problems

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.

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.