Avalanche Forecast
Issued: Dec 9th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
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Avalanche Canada
Danger will increase throughout the day with the approaching storm. Pay close attention to changing conditions, especially at higher elevations.
Summary
Confidence
Moderate - Uncertainty is due to the complexity of the snowpack’s structure.
Weather Forecast
A frontal system will arrive on Friday night and bring strong wind and new snow.
THURSDAY NIGHT: Mostly cloudy, no significant precipitation, moderate wind from the west, treeline temperatures around -12 C.
FRIDAY: Increasing cloud with afternoon flurries bringing up to 5 cm of snow, strong wind from the southwest with gusts to 70 km/h, treeline temperatures increase to -8 C.
SATURDAY: Snowing throughout the day with a total of 15-25 cm, strong wind from the south with gusts to 90 km/h, treeline temperatures around -5 C.
SUNDAY: Mix of sun and cloud, no significant precipitation, light to moderate wind from the south, treeline temperatures around -8 C.
Avalanche Summary
While there have been no avalanches reported in the past few days, there was likely some avalanche activity in the alpine during Wednesday's storm. Wind slab avalanches remain a concern at treeline and alpine elevations.
There were two human triggered avalanches involving persistent weak layers earlier this week. One was a size 2 avalanche triggered in a north-facing bowl near Barkerville. This avalanche is suspected to have occurred on a 50 cm deep surface hoar layer. The other was triggered near McBride and released on a steep rocky slope near treeline (see this MIN report). The failure layer was likely an early season crust/facet layer.
Snowpack Summary
Storms over the past week delivered a total of 20-40 cm of new snow. The snow at higher elevations has been heavily wind affected, with scoured surfaces on windward terrain and wind slabs on leeward terrain. There are a few potentially concerning layers underneath the recent snow including isolated layers of surface hoar around treeline and a slippery crust below 1800 m. Regardless of the elevation, be alert to areas where the recent snow feels stiff or slabby.
An early season crust layer with some weak snow around it can be found 100-250 cm deep in the alpine. There is also evidence of a weak surface hoar layer 50 cm deep in the Barkerville area.
Terrain and Travel
- Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
- Caution around convexities or sharp changes in terrain.
- Avoid areas where the snow feels stiff and/or slabby.
- Be alert to conditions that change with elevation and wind exposure.
Problems
Wind Slabs
Recent weather has likely left unstable slabs at upper elevations, especially on the leeward side of ridges. Pay attention to the look and feel of the surface snow, as slab formation could also become more widespread.
Aspects: North, North East, East, South East.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A few recent reports of avalanches have raised concern about buried weak layers in the Cariboos. The main concern is a buried surface hoar layer near Barkerville, especially on north-facing slopes. We suggest conservative terrain selection as these layers could remain reactive with the added weight of new snow.
Aspects: North, North East, East, North West.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Dec 10th, 2021 4:00PM
