Avalanche Forecast
Issued: Dec 9th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
shorton,
Avalanche Canada
Remain cautious in steep terrain at higher elevations. Weather trends suggest the snowpack has gained strength, but there is uncertainty about the likelihood of triggering large avalanches.
Summary
Confidence
Moderate - Confidence is due to a stable weather pattern; little change is expected for several days. Uncertainty is due to limitations in the field data.
Weather Forecast
A building ridge will bring cool and clear conditions for the next few days.Â
WEDNESDAY NIGHT: Partly cloudy, moderate northwest wind, alpine temperatures drop to -10 C.
THURSDAY: Mix of sun and cloud, light wind, high temperatures around -5 C.
FRIDAY: Mix of sun and cloud, moderate west wind, high temperatures around -7 C.
SATURDAY: Mix of sun and cloud, moderate northwest wind, high temperatures around -10 C.
Avalanche Summary
Reports from Tuesday suggest there were some cornices failures that triggered loose avalanches on the slopes below (see this MIN report). There were also some wet loose avalanches near valley bottoms. While the warm wet storm earlier this week likely caused some natural storm and wind slab avalanches, these problems have become less likely.
There was an avalanche fatality near Pine Pass on Saturday, November 28. Reports indicate a size 3 deep persistent slab avalanche at approximately 1600 m elevation on a northeast aspect. The avalanche may have run on a weak layer of faceted crystals sitting on a crust that was buried in early November.
Snowpack Summary
The warm storm earlier this week has reshaped the snowpack. The alpine is heavily wind-affected with quickly strengthening wind slabs. Below 1500 m the snowpack is rain soaked and likely forming a thick surface crust. At elevations in between there is 10-30 cm of recent snow sitting above old interfaces. There is a chance the snowpack at these intermediate elevations could be bonding poorly, but weather trends suggest they should be strengthening.
The main uncertainty right now is whether there is weak snow around the crust that formed in early November. This layer is now buried 50-150 below the surface, and with little data is is best to remain cautious around large high consequence slopes, especially if they are thin and rocky.Â
Snow depths are approximately 150 cm in the northwest of the region (Pine Pass), 180 cm in the south (Renshaw, Kakwa) and 100 cm in the the northeast (Tumbler Ridge).Â
Terrain and Travel
- Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
- Avoid steep convexities or areas with a thin, rocky, or variable snowpack.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Wind Slabs
Triggering wind slab avalanches remains possible at upper elevations, so pay attention to recent wind loading patterns.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
Weak snow around the early November crust was a problem earlier this season. The layer is now buried 50-150 cm deep. Recent weather trends suggest it is becoming less likely to trigger a large avalanche on this layer, however given the limited field observations to confirm this it's best to approach big slopes with caution.
This layer is most likely to be reactive to human triggers on south facing slopes and on steep, shallow, rocky, snowpack areas in the alpine.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 11th, 2020 4:00PM
