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Avalanche Forecast

Archived

Feb 12th, 2021–Feb 13th, 2021

Alpine
Natural avalanches possible, human triggered probable.
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.

A little warmer, but still windy! Use caution when transitioning into wind affected terrain. There could be potential for wide propagation on large terrain features.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

FRIDAY NIGHT - Partly cloudy / strong to extreme south east wind / alpine high temperature near -12

SATURDAY- Partly cloudy / strong southerly / highs near -8

SUNDAY - Overcast, possible light snow, strong south wind, highs near -9

MONDAY - Cloudy, flurries, moderate to strong west wind, -8

Avalanche Summary

In the Terrace vicinity, natural wind slabs to size 2 were reported on various wind loaded and cross loaded aspects . Wind slabs were also reactive to human triggering with ski cuts in the size 1-1.5 range.

In both the far north and in the south of the region, a few natural size 3 avalanches from big features occurred.

On Tuesday wind slabs up to size 2 were reported by various operators. The northern part of the region had the biggest reported events with windslabs up to size 2.5 on the late January interface.

On Monday, skiers were able trigger unsupported pillows failing on surface hoar down 25-40 cm near Terrace. In the north of the region, skiers found reactive wind slabs in immediate lee features in the alpine. 

Snowpack Summary

Continued outflow winds are building wind slabs (where snow is just not sublimating) and reverse loading features. Hard slabs, scoured slopes and sastrugi will be present where outflow effects are the strongest. In more sheltered zones, reactive wind slabs will be found on a variety of aspects and elevations due to terrain effects and the 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.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • 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.