Avalanche control work on Thursday triggered slabs up to size 3 and flights found a natural cycle up to sz 3.5.
While natural activity has tapered off, the potential for human triggering remains.
Expect Avalanche Hazard to remain elevated through the weekend as the winds pick up and temperatures rise.
30-60 cm of storm snow added a significant additional load to the snowpack, with strong winds contributing to the formation of slabs. These will remain reactive in the short term and can be found on all aspects at treeline and above.
Most of the avalanches observed on Thursday stepped down to a midpack layer of facets that was buried on Nov 22. These facets are reactive where a slab exists above them and seem touchier when they are sitting over a sun or temperature crust that formed a few days earlier in some areas.
There is a lot of snow hanging from cliff faces, which can catch people off guard in gullies and extreme terrain and act as a trigger to the widespread slab problems. Elevated winds will keep this problem active through the weekend.
Thursday, explosive avalanche control on Mounts Whymper and Field produced many sz 2.5 and a few sz 3 avalanches. Crowns averaged 60-80cm but were up to 100cm deep with most failing midpack on the November 22 interface.
Flights found evidence of a widespread avalanche cycle with many events exceeding sz 3. Significant naturals included a sz 2.5 over the ice on Bourgeau Left-Hand and a sz 3.5 on the Whymper South route that took almost all of the snow from all slopes in the basin.
30-60cm of storm snow arrived this week with strong SW winds. Fresh wind slabs are prevalent in the alpine and into treeline up to 60cm deep. 60-80cm of snow sits over a mid-November interface of facets that are particularly touchy when they are associated with a sun or temperature crust that exists in some places well into the alpine. Further down, the November 13 rain crust extends to 2100-2300m.
Treeline temperatures are expected to remain near -5C Saturday morning with west winds shifting SW and increasing to strong in the alpine. Trace amounts of precip as temperatures climb above freezing at 2000m.
An above-freezing layer is forecast to keep 2000m temperatures near zero overnight Saturday with light precip expected Sunday.
For more info, click here for Environment Canada tables.
