Strong winds, additional precipitation, and rising freezing levels make the trifecta of avalanche hazard.
Make conservative terrain choices and avoid overhead hazard.
A persistent weak layer consisting of facets over a hard crust still has the potential to produce large, destructive avalanches. Avoid overhead hazard; remote triggering is a concern with this layer.
Storm slabs will likely remain rider triggerable, especially on north and east aspects at treeline and above. Storm slabs could step down to deeper layers, resulting in large avalanches.
A significant increase in temperature combined with new snow and possible rain will make loose wet avalanches quite likely. On south facing slopes, a crust sits under the recent snow which can act as a perfect sliding surface.
Last weekend, numerous large (up to size 3) avalanches were reported, both natural and human triggered, all suspected to have failed on the late January crust/facet layer. They were mostly at treeline, although two human triggered avalanches were in open, alpine or alpine-like terrain.
Looking forward, we expect that humans are likely to trigger avalanches in the recent storm snow, that could become larger and more destructive if they step-down to deeper weak layers.
Up to 40 cm of moist snow has fallen in the alpine, rapidly tapering to 5 cm below treeline. This new snow, combined with continued strong west winds, makes for deeper and more reactive slabs in leeward and cross-loaded terrain.
Rain has saturated the top 10 to 20 cm below treeline turning the snow isothermal.
The new and settling snow overlies a melt-freeze crust on solar aspects and lower elevations, and wind-affected surfaces at higher elevations.
50-150 cm below the snow surface on north aspects, two persistent weak layers can be found, buried in late January and early February. These weak, sugary facets (over a crust on the late January layer), have the potential to produce large, destructive avalanches.
Friday Night
Cloudy. 2 to 4 cm of snow. 60 km/h west ridgetop wind. Treeline temperature -1 °C. Freezing level 1500 m.
Saturday
Cloudy. 3 to 10 mm of precipitation as snow or rain at treeline. 70 km/h west ridgetop wind. Treeline temperature -1 °C. Freezing level 1700 m.
Sunday
Mostly cloudy. 10 to 20 cm of snow. 70 km/h southwest ridgetop wind. Treeline temperature -3 °C. Freezing level 1500 m.
Monday
Mostly cloudy. 4 to 25 cm of snow. 40 km/h west ridgetop wind. Treeline temperature -9 °C.
More details can be found in the Mountain Weather Forecast.
