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Avalanche Forecast

Archived

Feb 9th, 2020–Feb 10th, 2020

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

Regions

Northwest Inland.

Certain slopes have potential for very large, destructive, persistent slab avalanches and even brief periods of exposure to the strengthening February sun may have a destabilizing affect. Carefully evaluate the snowpack and terrain before committing to avalanche terrain.

Confidence

Low - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

We’re moving into a period of high winds with dribs/drabs of precipitation.

SUNDAY NIGHT: Freezing level around 400 m, strong northwest wind, 1 to 5 cm of snow possible.

MONDAY: Overcast, freezing level around 700 m, strong west/southwest wind, trace of snow possible during the day, 2 to 8 cm expected Monday Night.

TUESDAY: A few clouds, freezing level at valley bottom, moderate to strong northwest wind, trace of snow possible.

WEDNESDAY: Scattered cloud cover, freezing level near valley bottom, moderate to strong southwest wind, trace of snow possible.

Avalanche Summary

Over the weekend some touchy wind slabs were observed, check out the details here. The very large avalanche observed from Smithers is scary and is what we're pointing to in our Persistent Slab Avalanche Problem. We're glad that no one was harmed in this snowmobile triggered persistent slab avalanche. There are more impressive photos in the Northwest Inland MIN list which you can find here.

Isolated wind slabs and dry loose avalanches to size two were also reported on northerly aspects. A few natural very large (size 3) avalanches were observed in alpine features in the central portion of the region over the last few days too.

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 continues to be 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 Smithers, 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.