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Avalanche Forecast

Archived

Dec 21st, 2023–Dec 22nd, 2023

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 unlikely, human triggered possible.
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.

Regions

Northwest Coastal, Boundary, Stewart, Ningunsaw, Ningunsaw, Ningunsaw.

Wind slabs have formed at higher elevations, approach ridgelines and mid slopes rollovers with caution.

Confidence

Moderate

Avalanche Summary

Avalanche activity on Thursday was limited to north facing slopes at treeline and above. Natural avalanches were reported to size 2 in steep terrain features. One wind slab was remotely triggered, indicating touchy conditions.

Snowpack Summary

20-30 cm of storm snow has likely been redistributed by southwesterly winds into wind slabs on north and east facing slopes. There may be a spotty layer of surface hoar about 15-30 cm below the snow surface in sheltered terrain, at treeline and below.

A layer of facets buried at the end of November can be found 100 to 200 cm below the surface. The snowpack depth varies between 150 and 250 cm at treeline.

Weather Summary

Thursday Night

Cloudy with 5-10 cm of snow, southwest winds 30-50 km/h. Freezing levels at valley bottom.

Friday

Cloudy with up to 5 cm of snow, southerly winds 20-40 km/h, treeline temperature -7 °C. Freezing levels at valley bottom.

Saturday

Mainly cloudy with up to 10 cm of snow, southerly winds 50-80 km/h. Freezing levels rise to 500 m, treeline temperature -5 °C.

Sunday

Cloudy with moderate snowfall. Southerly winds, 60-90 km/h. Freezing levels rise to 1000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.

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.