Wind slabs are likely to be encountered at upper elevations and will likely be reactive to human triggering. Choose conservative terrain, especially at upper elevations.
25-40 cm of recent storm snow and strong west winds have formed wind slabs in many areas. These slabs will be the most reactive in wind loaded areas.
Weak snow at the bottom of the snowpack hasn't gone away. Evidence of deep persistent slab avalanches has been focused in the Sparwood-Elkford area over the past month. Human triggering is most likely around steep rocky terrain features, or anywhere the snowpack is thin and weak. Cornices have grown large and loom over many ridge lines, a failing cornice could initiate a deep persistent slab when it impacts the slope below.
TUESDAY NIGHT- Mainly cloudy with flurries, 5-10 cm / west wind, 30-60 km/h / alpine low temperature near -7
WEDNESDAY- Cloudy with sunny periods and flurries, 5 cm / west wind, 40-60 km/h / alpine high temperature near -7
THURSDAY- Cloudy with sunny periods / northwest wind, 10-30 km/h / alpine high temperature near -11
FRIDAY- Mainly cloudy with flurries, 5 cm / east wind, 20-40 km/h / alpine high temperature near -15
With new snow and wind in the forecast, wind slabs will be building at upper elevations and may become more reactive throughout the day on Wednesday. Cornices are also growing large with this weather pattern and a cornice failure could trigger a wind slab avalanche on the slope below.
In the neighbouring Waterton Lakes National Park region, there were several natural loose dry avalanches up to size 1.5 reported on Monday.
In the neighbouring Lizard Range on Sunday, loose dry and soft slab avalanches were sensitive to human triggering and explosive avalanche control work to size 1.5. These avalanches were 10 to 20 cm in depth, running fast and far.
5-10 cm of snow on Tuesday night brings total recent storm snow totals to 25-40 cm. Strong west winds are promoting continued wind slab development. The new snow sits on wind slabs in exposed areas, and a sun crust on solar aspects (south through west facing slopes). Melt-freeze crusts extend up to about 1900 m on other aspects.
A thick crust with facets on it currently sits 40-80 cm below the surface and can be found up to 2100 m. The middle of the snowpack is generally strong, but the base of the snowpack contains basal facets that are most prominent in shallow rocky start zones.
