Avalanche Forecast

Issued: Dec 7th, 2021 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Wind Slabs and Deep Persistent Slabs.

Avalanche Canada shorton, Avalanche Canada

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Conservative terrain decisions are strongly recommended due to new snow, wind, and uncertainty about the strength of the snowpack.

Summary

Confidence

Moderate - Uncertainty is due to limitations in the field data. A small change in the upper snowpack could dramatically change avalanche conditions.

Weather Forecast

A cold front will bring gusty winds and 15-40 cm of low density snow on Wednesday.

TUESDAY NIGHT: Cloudy with flurries bringing 15-25 cm of low density snow, strong with from the southwest with gusts to 80 km/h, treeline temperatures around -10 C.

WEDNESDAY: Flurries easing throughout the day with another 5-15 cm of low density snow, cloudy skies, strong wind from the west with gusts to 80 km/h, treeline temperatures around -10 C.

THURSDAY: Cloudy with light flurries and no significant precipitation, moderate to strong wind from the west, treeline temperatures around -12 C.

FRIDAY: Cloudy with light flurries bringing up to 5 cm of snow, strong wind from the southwest, treeline temperatures around -10 C.

Avalanche Summary

While reports are limited, there have been two human triggered slab avalanches over the past few days. 

One was a size 2 avalanche triggered in a north-facing bowl in Barkerville on the weekend. This avalanche is suspected to have occurred on a 50 cm deep surface hoar layer that our field team also observed in that area.

The other was triggered on Monday near McBride and from the photos in this MIN report released on a steep rocky slope near treeline. The failure layer is unknown, but could be the early season crust/facet layer. This layer was the culprit in a few very large (size 3) naturally triggered avalanches in the Valemount - Blue River corridor last week. While this layer likely needs a heavy trigger like a cornice collapse, human triggering may be possible on thin rocky slopes.

Snowpack Summary

With 15-40 cm of fresh snow in the forecast, we can expect a total of 30-60 cm of low density from the past week. The surface snow should remain loose in sheltered terrain, but with strong winds in the forecast, we expect extensive blowing snow and the formation of fresh wind slabs at upper elevations. At elevations below 1800 m, this snow sits above a crust, and there is some concern about the bond of the snow to this crust. 

An early season crust layer with some weak snow around it can be found 100-250 cm deep in the alpine, but may be more shallowly buried in some areas. See the Avalanche Details for some suspicious activity involving this layer. There is also evidence of a weak layer of surface hoar 50 cm deep in the Barkerville area. 

Extra caution should be taken at this time with uncertainty about these buried weak layers and the added load of the new snow.

Terrain and Travel

  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Avoid areas where the snow feels stiff and/or slabby.
  • Be alert to conditions that change with elevation and wind exposure.

Problems

Wind Slabs

An icon showing Wind Slabs

New snow and strong wind will form unstable wind slabs. These conditions will most likely be found on the leeward side of ridges, but pay close attention to the look and feel of the surface snow as slab formation could be more widespread.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

A few recent reports of avalanches have raised concern about buried weak layers in the Cariboos. This includes a buried surface hoar layer observed near Barkerville and some avalanches on early season crusts in other parts of the region.

We suggest conservative terrain selection as these layers could become more reactive with the added weight of new snow.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Dec 8th, 2021 4:00PM