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Avalanche Forecast

Archived

Feb 14th, 2021–Feb 15th, 2021

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

Shifting wind direction and potential for new snow will keep danger elevated on Monday. Wind slabs sitting on cold, sugary faceted surfaces may take longer to bond than we are used to. There may be potential for wide propagation on bigger terrain features.

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

SUNDAY NIGHT - Overcast, 7-15 cm, light to moderate south west, low -9

MONDAY - Cloudy, 5-7 cm, moderate to strong west wind, -8

TUESDAY- Cloudy, trace snow amounts, moderate north west wind, high near -5

WEDNESDAY- Afternoon clearing possible, wind switching from north west to south east, high near -5

Avalanche Summary

Natural wind slabs to size 2 have been reported on various wind loaded and cross loaded aspects due to the outflow wind cycle. Wind slabs have also been reactive to human triggering with ski cuts in the size 1-1.5 range.

On Saturday explosives control around the region triggered cornice and wind slabs, mostly in the size 1-2 range with the odd larger result with big cornices.

It is worth remembering that skiers were able trigger unsupported pillows failing on surface hoar down 25-40 cm near Terrace last week, although there are no recent reports of avalanches failing on this layer, it is still propagating in some snowpack tests.

Snowpack Summary

New snow and moderate to strong westerlies may be building new wind slabs. Previous outflow winds have built wind slabs and reverse loaded features. Hard slabs, scoured slopes and sastrugi will be present where outflow effects were the strongest. In other places reactive wind slabs can be found on a variety of aspects and elevations due to terrain effects and the recent variable wind directions.

Cold temperatures are encouraging surface faceting of the upper snowpack. The late January interface is down 30-70 cm, this consists of surface hoar in sheltered locations, a crust on solar features, and facets and stiff wind affected snow at upper elevations. Below treeline, 10-30 cm of snow sits above isolated pockets of surface hoar and a crust that is more prominent on solar aspects. 

The mid-pack seems to be well settled. Deep persistent layers appear to have mostly become unreactive, with the exception of the Bear Pass area and the far reaches south of Kitimat. 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • 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.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.

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.