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Avalanche Forecast

Archived

Jan 6th, 2023–Jan 7th, 2023

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

Regions

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

Wind, snow, and warm temperatures and forming fresh and reactive wind slabs in the alpine and treeline. Seek out sheltered areas where you can avoid wind slabs and find good riding.

Concern for buried weak layers warrants conservative terrain choices with an avoidance of steep and convex slopes.

Confidence

Moderate

Avalanche Summary

As winds increased on Thursday, several natural and one human-triggered wind slabs (size 1-2) were observed in the alpine.

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 meter 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

Friday night

Cloudy with scattered flurries, 5-10 cm of accumulation. Alpine temperatures drop to a low of -1 °C. Ridge wind 20 km/h occasionally gusting to 60 km/h. Freezing level around 900 meters.

Saturday

Flurries, 5-10 cm of accumulation. Alpine temperatures reach a high of 0 °C. Ridge wind southeast 30-70 km/h. Freezing level around 700 meters.

Sunday

A mix of sun and cloud. Alpine temperatures reach a high of -1 °C. Ridge wind east 10-20 km/h. Freezing level rises to 800 meters.

Monday

A mix of sun and cloud. Alpine temperatures reach a high of -3 °C. Mostly light southeast ridge wind occasionally gusting to 30 km/h. Freezing level around 400 meters.

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.