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Avalanche Forecast

Archived

Apr 2nd, 2023–Apr 3rd, 2023

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

Regions

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

Recent new snow combined with wind has likely promoted fresh wind slab development at upper elevations.

Confidence

High

Avalanche Summary

A widespread avalanche cycle occurred yesterday, with small and large (size 2) storm slab, cornice fall, loose dry, and loose wet avalanches occurring throughout the region.

Skiers in the Shames backcountry triggered a slab avalanche 60 cm deep that occurred on a wind-loaded, north-facing slope. You can read the details here.

Several large (size 2) cornice falls occurred in the past week, most of which have not triggered slabs on the slopes below. However, there are a few exceptions where cornices did trigger large avalanches, including two avalanches north of Stewart on Tuesday (100 to 250 cm deep) and one avalanche north of Terrace on Thursday (30 cm deep).

Snowpack Summary

Most areas saw 15-20 cm of new snow in the alpine yesterday, with up to 40 cm near Stewart. Snow totals rapidly taper off as you go down in elevation. New snow has formed reactive slabs in specific areas, such as near ridgecrest in the alpine.

In most areas this snow has covered a melt-freeze crust, except on shady slopes above 1500m where the snow has remained dry over the past week.

In most areas the lower snowpack is generally strong and well bonded. In outlying northern reaches of the region, basal facets may exist which are currently considered dormant. This layer may become active with abrupt changes to the snowpack, such as rapid loading (heavy snowfall or rain) or prolonged warming.

Weather Summary

Sunday night

Partly cloudy, light to moderate northwest wind, freezing level dropping to valley bottom in most areas.

Monday

Mix of sun and cloud, chance of flurries with accumulations up to 5cm, light to moderate northwest wind, treeline temperatures high of -3 °C, freezing level rising to 700m.

Tuesday

Mostly sunny with increasing cloud, chance of flurries in the afternoon with trace accumulations, light to moderate west and southwest wind, treeline temperatures -5 °C to 0 °C, freezing level 500 rising to 1100m.

Wednesday

Mostly cloudy, 5 -10 cm of accumulation, moderate to strong south and southwest wind, treeline temperatures -5 °C to 1 °C, freezing level 500 rising to 1200m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Seek out sheltered terrain where new snow hasn't been wind-affected.
  • Carefully evaluate steep lines for wind slabs.
  • Caution around slopes that are exposed to cornices overhead.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.