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Avalanche Forecast

Archived

Mar 9th, 2021–Mar 10th, 2021

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 and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.

Regions

Northwest Coastal.

Increasing wind has the potential to form new wind slabs.

Confidence

High -

Weather Forecast

TUESDAY NIGHT: Clear skies, 40 km/h north wind, alpine temperature -7 C.

WEDNESDAY: Clear skies, 20 to 40 km/h northeast wind, alpine temperature -7 C.

THURSDAY: Increasing clouds with afternoon snowfall, accumulation 5 cm, 60 km/h southwest wind, alpine temperature -6 C.

FRIDAY: Cloudy with snowfall, accumulation 30 to 50 cm, 30 to 60 km/h southwest wind, alpine temperature -5 C, freezing level 800 m.

Avalanche Summary

A persistent slab avalanche was triggered on Monday along the Skeena corridor/Highway 16 west of Terrace, releasing on the persistent weak layer described in the Snowpack Summary. Otherwise, no new avalanches were observed.

Snowpack Summary

Moderate to strong northerly wind is forecast Monday night, which could load atypical slopes in exposed terrain. Wind slabs have the potential to form anywhere snow is available to be transported. In sheltered terrain, around 30 cm of soft snow may be found.

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.
  • Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
  • 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.