Increased southerly winds combined with recent storm snow may form new wind slabs at treeline and above.
Rider-triggered avalanches are possible.
15-40 cm of recent storm snow may be easily transported by moderate to strong southwest wind. Fresh wind slabs may build on leeward slopes.
Slabs may be more reactive where they sit above buried surface hoar or crust layer that exists 40-50 cm deep.
A weak layer of facets exists near the base of the snowpack. The likelihood of human triggering is low given the layer's depth.
Suspect terrain for human triggering includes steep, shallow, and rocky terrain where the snowpack transitions from thin to thick.
On Tuesday, numerous storm and wind slab avalanches were reported up to size 1.5. These failed naturally and were human-triggered. Additionally, several natural size 2 avalanches were seen on east-facing aspects near 2400 m and surface hoar was the suspect failing layer.
On Monday, natural solar-induced slab avalanches were reported up to size 2.5 and the recent storm snow continued to be reactive to rider triggering up to size 1.5. Reports indicate that the Selkirks seem to be the most reactive with rider remote-triggered slabs in the upper 50 cm of snow. These are failing on a surface hoar layer buried near the end of March or a crust on solar aspects. These avalanches were primarily on north and east aspects from 1700 m to 2200 m.
This MIN Report from Sunday indicates what is mentioned above.
At higher elevations, 15-40 cm of mostly soft storm snow is settling over a widespread, crust except for north-facing slopes at treeline and above, where it sits on old, faceted surfaces, and surface hoar in sheltered terrain. A surface hoar layer (down 50 cm) was surprisingly reactive to human triggers in the Selkirks on Monday, especially on northeasterly slopes from 1700 m to 2100 m.
Forecast moderate to strong southwest wind will likely build fresh wind slabs on leeward slopes and behind terrain features.
The mid-snowpack is generally strong but the lower snowpack is a different story. The November facets are still prominent at the base of the snowpack. This layer remains a concern in rocky, shallow, or thin to thick snowpack areas at treeline and above.
Wednesday Night
Clear periods. Ridgetop wind 15 km/h from the southwest and freezing level falling to valley bottom. Treeline low around -9°C.
Thursday
Cloudy. Possible trace of snow. Ridgetop wind 15-35 km/h from the southwest. Freezing level rising to 1700 m. Treeline high around -3°C.
Friday
Cloudy with new snow 5-15 cm. Ridgetop wind 25-40 km/h from the southwest. Freezing level rising to 1900 m.
Saturday
Cloudy with possible sunny periods and flurries up to 5 cm. Ridgetop wind 15 km/h gusting to 50 km/h from the southwest. Freezing level 700 m in the morning, rising to between 1700 m.
More details can be found in the Mountain Weather Forecast.
