Avalanche Forecast

Archived

Apr 9th, 2023–Apr 10th, 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 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.

Continue to make conservative terrain choices as the snowpack adjusts to the significant new snow load.

Confidence

Moderate

Avalanche Summary

On Saturday, natural and controlled storm slabs and loose wet avalanches were reported, size 1-2 in the south of the region.

On Friday numerous persistent slab avalanches to size 2.5 were reported near Stewart. Avalanches were triggered both naturally and by riders (some remotely) and on a variety of aspects and elevations, running on a weak layer buried March 31st.

Snowpack Summary

30-60 cm of recent snow fell dry above 1500 m and as rain below 700 m. At upper elevation, the new snow continues to be redistributed by southwest winds into wind slabs on north-to-east-facing slopes. The recent snow sits over wind-affected surfaces, weak faceted crystals or a crust on south-facing slopes.

A weak layer buried at the end of March sits 50-80 cm deep in most areas (potentially over 1m deep in immediate coastal terrain). It includes facets and surface hoar in shaded areas, and a melt-freeze crust elsewhere. This layer has shown limited reactivity within the past week.

The mid and lower snowpack are considered generally strong and well-bonded. In far northern reaches of the region, basal facets may exist which are currently considered inactive. 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

10-15 cm of new snow. Strong southwest wind. Alpine low -7. Freezing levels around 800 m.

Monday

Around 5 cm of new snow. Moderate southwest winds. Alpine high -2 C. Freezing levels around 1000 m.

Tuesday

A mix of sun and cloud. Light northwest wind. Alpine high -2 C. Freezing levels around 1000 m.

Wednesday

Cloudy. Moderate southwest winds. Alpine high -5 C. Freezing levels around 800 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Continue to make conservative terrain choices while the storm snow settles and stabilizes.
Stick to simple terrain features and be certain your location isn't threatened by overhead hazard.
Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
Avoid freshly wind loaded terrain features.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.