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Avalanche Forecast

Archived

Feb 10th, 2020–Feb 11th, 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.

We're seeing a lot of very large destructive avalanches releasing naturally and being triggered by humans, these can only be managed by avoiding travel on the bigger more complex terrain features. Wind slabs remain an active problem, especially near ridge crest.

Confidence

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

Weather Forecast

The forecast period is marked by high winds accompanied by dribs & drabs of precipitation.

MONDAY NIGHT: Freezing level around 1200 m, strong to extreme southwest wind, 2 to 10 cm of snow expected.

TUESDAY: A few clouds, freezing level around 600 m, but it could extend as high as 1200 m, strong northwest wind, no significant snowfall expected.

WEDNESDAY: Broken cloud cover, freezing level at valley bottom, moderate to strong southwest wind, trace of snow possible during the day, 2 to 8 cm possible Wednesday Night.

THURSDAY: Overcast, freezing level around 700 m, moderate to strong southwest wind, trace of snow possible.

Avalanche Summary

Since February 3rd there have been many very large destructive avalanches failing deeply on buried surface hoar and crust/facets at the bottom of the snowpack. The bulk of the activity is above treeline on north through east facing aspects, but all alpine slopes that have not yet avalanched need to be treated as suspect. A few examples of the most recent activity are reported here:

Feb 9: Very large avalanche on the Kathlyn Face near Smithers. Details/Photos here and here.

Feb 9: Large avalanche in the French Peak Complex. Details/Photos here.

Feb 9: Very large avalanche near the Pine Creek Trail. Details/Photos here.

Feb 8: Large snowmobile triggered avalanche in the Babines. Details/Photos here.

Feb 8: Very large avalanche on Mt. Elmstead above Silver King Basin Trail in the Babines. Details/Photos here.

Persistent slabs are not the only problem either, over the weekend some touchy wind slabs were observed, check out the details here. 

Snowpack Summary

Open terrain continues to be heavily affected by strong wind from the west which has been actively loading lee terrain features and seems to be pushing the persistent slab problem to it's breaking point. Crusts can be found on the surface up to roughly 1200 m and on open south-facing slopes. Weak layers formed during cold weather in January have reactivated and have consistently been producing very large avalanches since February 3rd.

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, the Kispiox and the Babines, but persistent weak layers could be a problem on slopes anywhere in the region. 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
  • Be aware of the potential for large, destructive avalanches due to the presence of deeply buried weak layers.
  • Avoid lingering or regrouping in runout zones.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.