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Avalanche Forecast

Archived

Feb 7th, 2020–Feb 8th, 2020

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

Regions

Northwest Inland.

Certain slopes have potential for large persistent slab avalanches and the strengthening February sun may have a destabilizing affect. Carefully evaluate the snowpack and terrain before committing to avalanche terrain.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

We’re moving into a rather benign weather window for the next few days highlighted by clear skies and potentially strong wind for the later half of the weekend.

FRIDAY NIGHT: Freezing level at valley bottom, light northeast wind at most elevations, no significant precipitation expected.

SATURDAY: Clear skies, freezing level at valley bottom, moderate northwest wind that ramps up to strong northwest in the afternoon, no significant precipitation expected.

SUNDAY: Broken cloud cover, freezing level around 500 m, strong northwest wind, no significant precipitation expected.

MONDAY: Scattered cloud cover, freezing level around 800 m, moderate to strong west/northwest wind, no significant precipitation expected.

Avalanche Summary

On Thursday human triggered wind slabs to size 1.5 were reported at and above treeline on north and east aspects. Loose dry avalanches were also reported on steep south facing features below treeline. Some very large persistent avalanches have been reported over the past week. A size 3 avalanche was triggered by a snowmobiler in the Seaton area on Monday (northeast slope at 1800 m) and a size 3.5 avalanche was remotely triggered by a large snow machine near Kispiox on Saturday (southeast slope at 1700 m). Then on Wednesday, several size 2-3 avalanches were naturally triggered due to strong wind and mild temperatures. These avalanches have ran on both buried surface hoar layers and crust/facets at the bottom of the snowpack.

Some smaller (size 1) wind slabs were also triggered by riders on Wednesday.

Snowpack Summary

Open terrain has been heavily affected by strong wind from the west. Crusts can be found on the surface up to roughly 1200 m and on open south-facing slopes. Some areas continue to have issues with weak layers that formed during cold weather in January. Depending on location these layers may be composed of soft facets or surface hoar and are typically are buried 60-120 cm below the surface. Crust/facet layers also lurk at the base of the snowpack, especially in shallower (eastern) areas. The most recent signs of instability with these deeper layers have been around Hazelton and Kispiox, but persistent weak layers could be a problem on slopes anywhere in the region. 

Terrain and Travel

  • Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.
  • Be alert to conditions that change with elevation and sun exposure.

Problems

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.

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.