Avalanche Forecast

Archived

Apr 1st, 2023–Apr 2nd, 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.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

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

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

Confidence

High

Avalanche Summary

There were a few reports of size 1 storm slab avalanches on Saturday and Friday.

Several large (size 2) cornice falls have been observed 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 thick slabs) and one avalanche north of Terrace on Thursday (30 cm thick slab).

Snowpack Summary

10-20cm of new snow has accumulated at the end of the week, with deeper deposits in lee terrain. In most areas this snow has covered moist or crusty snow layers, except shaded terrain above 1500m where the snow has remained dry over the past week. The lower snowpack is strong and well bonded.

Weather Summary

Saturday night

Cloudy with clear periods, light to moderate southwest wind, treeline temperature around -8 °C with freezing level at valley bottom.

Sunday

Mix of sun and cloud , light west and northwest wind, treeline temperatures around -3 °C, freezing level 900m.

Monday

Mix of sun and cloud with isolated flurries, light to moderate northwest wind, treeline temperatures around -4 °C, freezing level 700m.

Tuesday

Mix of sun and cloud, moderate north wind, treeline temperatures around -2 °C, freezing level 1100m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

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.