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Avalanche Forecast

Archived

Mar 4th, 2023–Mar 5th, 2023

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.
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, South Bulkley, South Bulkley, Telkwa.

Seek out sheltered terrain and be suspicious of wind affected snow, like hard windslabs, cornices and cross-loaded slopes. Thin rocky areas will remain a concern in this complex snowpack.

Confidence

Moderate

Avalanche Summary

Our field team continues to observe numerous natural wind slab and cornice triggered avalanches up to size 2.

Last week, several large deep persistent slab avalanches were reported in the alpine, including a natural size 3 near Kispiox, a cornice-triggered size 2.5 at Hudson Bay and several explosive controlled size 2-3 near Ningunsaw.

Snowpack Summary

Extensive wind effect from all directions characterizes the snow surface at upper elevations. Exposed windward aspects have been scoured, pillows of deep snow and wind slabs may be found sitting unusually low down in start zones and lees. Cornices are large and can be found on a number of aspects from persistent variable winds.

In sheltered areas, 40-50 cm of recent snow may be sitting over a layer of small facets and cold snow that feels upside down

Several other crusts, layers of facets, or surface hoar can be found in the top 150 cm of the snowpack, but have not shown any avalanche activity or tests results yet.

The lower snowpack consists of weak, basal facets which may become active with any rapid change or shock to the snowpack, such as heavy loading or dramatic warming. Snowpack depths range from 60 to 280 cm at treeline.

Weather Summary

Saturday night

Possible flurries. Moderate easterly wind. Alpine low -15 ºC.

Sunday

Mostly sunny. Moderate easterly wind. Inversion up to -10 ºC in the alpine .

Monday

Mix of sun and cloud. Moderate southeasterly wind. Inversion in the morning. Alpine high -10 ºC.

Tuesday

Mix of sun and cloud. Possible flurries. Variable moderate wind. Alpine high -17 ºC.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.
  • Be especially cautious as you transition into wind affected terrain.
  • Stay off recently wind loaded slopes until they have had a chance to stabilize.
  • Be mindful that deep instabilities are still present and have produced recent large avalanches.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.

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.