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Avalanche Forecast

Archived

Mar 10th, 2021–Mar 11th, 2021

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.

Regions

Northwest Coastal.

The next storm rolls in on Thursday. Wind slabs are the primary concern for Thursday before storm slabs build.

Confidence

High -

Weather Forecast

WEDNESDAY NIGHT: Increasing clouds, 20 to 40 km/h west wind, alpine temperature -7 C.

THURSDAY: Cloudy with snowfall, accumulation 5 cm, 40 km/h southwest wind, alpine temperature -6 C.

FRIDAY: Cloudy with snowfall, accumulation 30 to 50 cm, 60 km/h southwest wind, alpine temperature -3 C, freezing level rising to 1000 m.

SATURDAY: Cloudy with snowfall, accumulation 60 cm, 30 km/h south wind, alpine temperature -2 C, freezing level 1100 m.

Avalanche Summary

No new avalanche observations were observed on Wednesday at the time of writing. Some avalanche activity was observed on southerly aspects on Tuesday during the heat of the day. A few cornices were also triggered, which did not trigger slabs on the slopes below.

Looking ahead, newly formed wind slabs will be the primary concern on Thursday. An avalanche cycle is expected to occur in the coming days if the forecast snow amounts hold true.

Snowpack Summary

An incoming storm will bring strong southwest wind and a bit of new snow on Thursday, forming wind slabs at treeline and alpine elevations. The new snow may overly feathery surface hoar on northerly aspects and in sheltered terrain features around treeline or a melt-freeze crust on southerly aspects and below treeline.

Around 100 to 200 cm overlies a persistent weak layers buried in mid-February that may still be a concern in parts of the region. The layer consists of feathery surface hoar crystals in areas sheltered from the wind and sugary faceted grains that formed during February's cold snap. Avalanche activity on this layer has mostly occurred west of Terrace along Highway 16 in the past week, but the layer could still be of concern anywhere it exists.

There are currently no layers of concern in the mid and lower snowpack.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.

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.