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Avalanche Forecast

Archived

Mar 14th, 2023–Mar 15th, 2023

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
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 Inland, Kispiox, Microwave-Sinclair, Ningunsaw, Ningunsaw, South Bulkley, South Bulkley, Telkwa.

Continue to assess for wind slabs in steep terrain at higher elevations.

Confidence

Moderate

Avalanche Summary

We received a report of a small (size 1) wind slab avalanche on north facing, steep terrain from Tuesday.

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

Snowpack Summary

Around 10 to 20 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. Wind has shifted from the north to the south meaning that wind slabs may be found on all aspects.

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

Tuesday Night

Cloudy with snowfall, accumulation 5 cm, 20 to 30 km/h south wind, treeline temperature -10 °C.

Wednesday

Cloudy with snowfall and periods of clearing, accumulation 5 cm, 30 km/h southwest wind, treeline temperature -9 °C.

Thursday

Cloudy with snowfall, accumulation 5 to 10 cm, 30 km/h south wind, treeline temperature -6 °C, freezing level rising to 1000 m.

Friday

Partly cloudy with no precipitation, 30 to 40 km/h southeast wind, treeline temperature -4 °C, freezing level 1000 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.