Avalanche Forecast

Thursday looks to be the calm before a pretty robust series of storms that begin to impact the area on Friday.

WEDNESDAY NIGHT: Freezing level at valley bottom, moderate west/southwest wind, 1 to 5 cm of new snow possible. 

THURSDAY: Overcast, freezing level at valley bottom, moderate to strong west/southwest wind, up to 5 cm of snow possible.

FRIDAY: Overcast, a bit of an inversion with below freezing temperatures at valley bottom and temperatures near 0 C up to about 1500 m, strong to extreme southwest wind, 10 to 25 cm of snow possible during the day with another 10 to 20 cm possible Friday night.

SATURDAY: Overcast, a bit of an inversion with below freezing temperatures at valley bottom and temperatures near 0 C up to about 1500 m, strong to extreme southwest wind, 8 to 15 cm of snow possible during the day with another 5 to 20 cm expected Saturday night. 

This wind slab avalanche from Tuesday is a great visual of the wind slab problem we're concerned about in the region.

Observations have been scant, but there were a few large human-triggered persistent slab avalanches in the neighbouring Cariboo region last weekend (on northeast slopes near treeline).

The persistent slab avalanche problem is now a low-probability/high-consequence situation. There were many notable avalanches between Dec 18-20 including natural, accidental, and remotely triggered avalanches up to size 2.5 at Pine Pass, Torpy, and Tumbler Ridge. There have not been any avalanches on persistent weak layers in the past week that we know of, however snowpack observations suggest these layers may still be reactive in certain isolated areas.

Open terrain is heavily wind affected with potentially reactive wind slabs on steep slopes. 30-50 cm of settled snow sits above a mix of interfaces that were buried in early December. In some (but not all) terrain these interfaces may be composed of weak surface hoar or weak crusts and facet layers, creating a persistent slab avalanche problem. We do not see a clear pattern in which parts of the region or which types of terrain this problem is still a concern. Between Dec 18-20 there was compelling evidence of this problem around Pine Pass, the McGregors, and Tumbler Ridge. This problem has not been found at Renshaw, but has been found in the surrounding areas near McBride. There is no recent information from Kakwa. Overall, uncertainty about these layers make it difficult to have confidence in challenging or complex avalanche terrain without very careful terrain evaluation and an in-depth understanding of local snowpack conditions.

Snow depths are in 150-250 cm around Pine Pass, the McGregors, and McBride and closer to 100-150 cm around Tumbler Ridge. In shallower areas along the eastern slopes there could be weak snow at the bottom of the snowpack that could be a concern in steep rocky alpine terrain.

• Use careful route-finding and stick to moderate slope angles with low consequences.
• Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
• Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
• Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.