Avalanche Forecast

Archived

Mar 15th, 2023–Mar 16th, 2023

Alpine

Natural avalanches unlikely, human triggered possible.

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Northwest Inland, Kispiox, Microwave-Sinclair, Ningunsaw, Ningunsaw, South Bulkley, South Bulkley, Telkwa.

Assess for wind slabs in steep terrain prior to committing.

Confidence

Moderate

Avalanche Summary

A few storm slab avalanches were reported on Tuesday. A large load remotely triggered a large (size 2.5) avalanche, which occurred within the 20 cm of storm snow that has accumulated since the weekend. Otherwise, the storm snow was sluffing in steep terrain, particularly where it overlies a hard crust on sun-exposed slopes.

Looking forward, progressive snowfall with southwest wind could continue to form slabs that could be touchy to riders.

Snowpack Summary

Around 15 to 25 cm of snow overlies large (10 mm) surface hoar crystals in terrain sheltered from the wind, wind-affected snow in wind exposed terrain, and a hard melt-freeze crust on sun-exposed slopes. Strong southwest wind means that the deepest deposits are likely found in lee terrain features near ridges.

The middle of the snowpack is strong and contains numerous hard crusts.

The lower snowpack is composed of weak basal facets. The layer is currently dormant but it may become active with any rapid change to the snowpack, such as rapid loading (e.g., heavy snowfall or rain) or prolonged and extensive warming. Avoiding thin and rocky slopes is still recommended. Cornices are also very large and a cornice failure could trigger this basal layer.

Weather Summary

Wednesday Night

Cloudy with light snowfall, accumulation 1 to 3 cm, 30 to 40 km/h southwest wind, treeline temperature -8 °C.

Thursday

Cloudy with light snowfall, accumulation 1 to 3 cm, 20 km/h southwest wind, treeline temperature -6 °C, freezing level rising to 1000 m.

Friday

Mix of sun and cloud with no precipitation, 30 km/h southeast wind, treeline temperature -4 °C, freezing level 1100 m.

Saturday

Mix of sun and cloud with no precipitation, 30 km/h southeast wind, treeline temperature -3 °C, freezing level 1200 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Carefully evaluate steep lines for wind slabs.
Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Conditions may have improved, but be mindful that deep instabilities are still present.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.