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Avalanche Forecast

Archived

Mar 7th, 2021–Mar 8th, 2021

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

Regions

Northwest Coastal.

Wind slabs may be triggered by riders at higher elevations. The consequence of triggering a deeper weak layer would be high.

Confidence

High -

Weather Forecast

SUNDAY NIGHT: Clear skies, 20 km/h south wind, alpine temperature -5 C.

MONDAY: Mix of sun and cloud, 10 km/h southwest wind, alpine temperature -5 C, freezing level 900 m.

TUESDAY: Clear skies, 20 km/h northwest wind, alpine temperature -6 C.

WEDNESDAY: Mix of sun and cloud, 30 km/h northwest wind, alpine temperature -5 C.

Avalanche Summary

A large (size 2.5) persistent slab avalanche released naturally west of Terrace along Highway 16 on Saturday out of a south-facing avalanche path. Some small (size 1 to 1.5) storm and wind slab avalanches were also triggered by riders. Otherwise, many loose wet avalanches were observed during the heat of the day.

Snowpack Summary

Moderate wind from variable directions has produced wind slabs in exposed terrain. The most likely place to find them is immediately adjacent to ridges at treeline and alpine elevations. Relatively mild conditions and sunny skies could weaken the snow on southerly aspects and make cornices more likely to be triggered.

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

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • 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.