Areas with the best snow (higher elevation, north-facing slopes) align with where large avalanches are possible. Travel in avalanche terrain warrants careful evaluation of wind-drifted snow and buried weak layers.
Incremental snowfall with strong southwest winds are building a reactive wind slab problem on immediate lee terrain features at upper elevations that may be prone to human triggering. Small wind slabs have the potential to step down to more deeply buried weak layers, creating larger avalanches.
25-50 cm cm of snow is settling over a layer of surface hoar on sheltered slopes near and above treeline. Recent warm temperatures have promoted cohesion in the slab above, priming this layer for human triggering. This persistent slab problem has been reactive primarily on north-facing slopes between 1900-2300 m.
Sunday night: Mostly cloudy, moderate west winds, freezing level dropping to 500 m.
Monday: Partly cloudy, moderate west winds, gusting strong at ridge-top, freezing level rising to 1600 m.
Tuesday: Mostly clear, 5-10 cm of snow overnight, with areas near Kootenay Pass seeing higher accumulations (10-20 cm), moderate southwest winds gusting strong at ridge-top, freezing level rising to 1800 m.
Wednesday: Mix of sun and cloud, up to 5 cm of snow, strong west winds, freezing level dropping to valley bottom by nightfall.
Since Thursday, numerous small (size 1-1.5) natural and human-triggered avalanches have been reported running on the February 22 surface hoar layer and breaking 25-40 cm deep. These avalanches occurred primarily on north-facing aspects between 1900-2250 m. Small wet loose activity was also reported on steep, sunny slopes during the warm temperatures on Thursday and Friday. In a few cases, these also initiated small slabs on the February 22 surface hoar.
On Thursday, a large (size 2), natural avalanche on an northwest aspect at 2100 m was thought to have stepped-down to the February 13 surface hoar layer.
Incremental snowfall and strong winds from the southwest are expected to continue to build reactive wind slabs at upper elevations.
A total 30-50 cm of snow is settling over a layer of feathery surface hoar in open, sheltered areas near and above upper tree line. Recent warm temperatures have promoted cohesion in the slab above, priming this layer for human triggering. This problem will be larger where the snow has been drifted by southwest winds into deeper deposits on lee features. Check out the latest forecaster blog that offers a deeper dive into these conditions.
An older layer of surface hoar from February 13th now sits 60-80 cm deep. This weak layer produced significant avalanche activity focused in the east of the region prior to the last storm. While it is likely bonding over time, there is uncertainty around remnant reactivity. Shallower avalanches may have the potential to step-down to this layer. The remainder of the snowpack is well settled.
