Wind and incremental snowfall on Thursday will begin to form our next layer of concern. Make note of the snow surface condition ahead of the snowfall. Buried weak layers remain possible to trigger.
Up to 15 cm of new snow is forecast to accumulate by late Thursday in favored areas. Moderate to strong southwest winds may redistribute the new snow into shallow slabs on isolated lee features.
Beneath 30-70 cm of snow from last weekend's storm, a layer of surface hoar and facets may linger as a persistent slab problem in isolated areas. The bigger concern is for a crust/facet layer that is buried closer to the ground from early November. Although it may be harder to trigger, the presence of this weak crust/facet combination appears more widespread. Large persistent slab avalanches may be possible to trigger on Thursday.
Temperatures return to more seasonal norms Thursday before an Atmospheric River delivers what is expected to be heavy precipitation starting Friday.
Wednesday night: Increasing cloud, up to 5 cm of new snow above 1000 m, moderate to strong southwest winds, freezing level dropping to 700 m.
Thursday: Overcast, 5 to 10 cm of snow, moderate to strong southwest winds, freezing level around 700 m.
Friday: Overcast, 20-35 cm of snow, strong south/southwest winds, freezing level rising to 1200 m.
Saturday: Overcast, 40-60 cm of snow, moderate to strong south/southwest winds, freezing level rising to 1600 m.
Although there are few observations, we suspect that wet loose avalanches ran during peak warming on Wednesday.
After the strong winds earlier in the week, small to large (size 1-2) wind slab avalanches released naturally in lee features.
During last weekend's storm, wind slabs from size 2 to 3 released naturally in steep alpine features near Bear Pass. Observers reported several persistent slabs releasing up to size 3.5, which likely failed on the November 3rd crust. Around Terrace, the Skeena and Bulkley valleys, moist avalanche debris from size 2 avalanches was observed. This makes sense as there was much less storm snow around Terrace when compared with the north.
Up to 15 cm of new snow is forecast to accumulate by late Thursday in favored areas. Moderate to strong southwest winds may redistribute the new snow into shallow slabs on isolated lee features.
A big swing in temperature over the past 24 hours has likely made drastic changes to the upper snowpack. What was left of last weekend's storm snow after Monday's strong winds is now likely capped with a widespread melt freeze crust. Track the condition of the snow surface on Thursday, as it is poised to become the next sliding layer with a powerful storm forecast for the weekend.
Last weekend's storm produced 30 to 70 cm of snow above 500 m. Strong to extreme southwest winds redistributed the snow into wind slabs and buried a layer of surface hoar and facets that formed in late November. This weak layer may linger as a persistent slab problem in isolated areas.
We're learning that another persistent slab problem, the early November crust, is widespread across alpine and treeline elevations. You will likely find it 25 to 50 cm above the ground.
The total snowpack depth is roughly 150 to 200 cm at upper treeline and alpine elevations. There could be weak snow developing near the ground in colder inland parts of the region. Observations are very limited, so please submit your observations to the Mountain Information Network!
