Stick to small slopes with limited consequences and no overhead hazard.
We have some uncertainty in the reactivity of persistent slabs, conservative terrain choices are the answer .
A persistent weak layer consisting of facets over a hard crust has been reactive in recent days. 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.
On Sunday numerous natural avalanches were observed on east through south aspects. These avalanches were generally at treeline and failed on the late January crust. A size 2 remotely triggered, persistent slab avalanche was also reported in Allison Pass. Details here.
On Saturday, an accident occurred on Thor Peak. 3 skiers were boot packing up a couloir when they triggered a size 3 persistent slab. Another size 2 persistent slab was also remotely triggered nearby.
20 to 40 cm of new snow is expected at upper elevations by Thursday morning, accompanied by strong west or southwest winds. Rain has saturated the top 10 to 20 cm below treeline.
This new snow overlies a melt-freeze crust on solar aspects and lower elevations, and wind-affected surfaces at higher elevations.
A persistent weak layer consisting of a crust/ facet layer from late January is currently buried 40 to 80 cm deep across the region. This layer has been reactive in recent days.
The snowpack below is strong and well-bonded.
Wednesday Night
Cloudy. 1 to 15 cm of snow. 40 km/h west ridgetop wind. Treeline temperature -4 °C. Freezing level 1300 m.
Thursday
Mostly cloudy. 1 to 2 cm of snow. 30 km/h west ridgetop wind. Treeline temperature -6 °C.
Friday
Cloudy. 10 cm of snow. 50 km/h west ridgetop wind. Treeline temperature -4 °C.
Saturday
Mostly cloudy. 5 to 15 cm of snow at treeline, rain below. 70 km/h west ridgetop wind. Treeline temperature -1 °C. Freezing level 1800 m.
More details can be found in the Mountain Weather Forecast.
