Avalanche Forecast
Issued: Dec 11th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Deep Persistent Slabs and Wind 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 - Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.
Weather Forecast
Cold arctic air pushes up along the eastern slopes of the Rockies this weekend.
FRIDAY NIGHT: Mostly cloudy, moderate northwest wind, temperatures drop to -15 C.
SATURDAY: Mix of sun and cloud with some isolated flurries along the eastern slopes, moderate northwest wind, steady temperatures around -12 C.
SUNDAY: Mix of sun and cloud, light southwest wind, high temperatures around -12 C.
MONDAY: Mostly cloudy, strong west wind, high temperatures around -10 C.
Avalanche Summary
In the wake of the storm earlier this week there were a few reports of wind slab avalanches and cornice failures in northeast facing terrain (see this MIN report from Wednesday). These wind slabs have likely gained strength since then.
While there have not been any recent reports of deep persistent slab avalanches, we can not rule out the possibility this problem still lurks in parts of the region. The crust near the bottom of the snowpack was the likely failure layer in a fatal avalanche near Pine Pass on Nov 28. With little recent information about this layer it is best to remain cautious around large high consequence slopes, especially if they are thin and rocky.
Snowpack Summary
The alpine is heavily wind-affected and lower elevations are capped by a hard rain crust (perhaps up to 1300 m). Sheltered areas at treeline may still have 5-20 cm of low density snow from earlier this week.
Snow depths are approximately 150 cm around Pine Pass, Torpy and McBride and 50-100 cm in the northeast around Tumbler Ridge. A widespread crust layer can be found at the bottom of the snowpack, and there remains to be uncertainty about if and where this layer is a problem. Recent observations from the McBride area suggest the snow is well bonded to this crust, however there is no recent information from northern parts of the region, such as Pine Pass and Tumbler Ridge, where this layer was a problem earlier this season.
Terrain and Travel
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
- Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Deep Persistent Slabs
We are uncertain about whether the early November crust remains to be a problem. Our limited information suggests this problem is more likely found around Pine Pass and the eastern slopes of the Rockies. However, given our lack of data, it's best to approach any big open slope with caution, especially those that are rocky and have variable snowpack depths.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
Triggering wind slab avalanches remains possible at upper elevations, especially on freshly wind loaded terrain features.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 12th, 2020 4:00PM
