New snow combined with reactive weak layers is creating dangerous conditions
Stick to low-angle slopes with limited consequences and no overhead hazard.
A persistent weak layer consisting of facets over a hard crust from late January has been very reactive in recent days. Avoid overhead hazard; remote triggering is a concern with this layer.
Up to 25 cm of new snow and wind will be forming reactive storm slabs. Thier size and sensitivity will increase throughout the day. These slabs will be most reactive in lee areas by ridgetops, and could step-down to deeper weak layers.
Monday
Many natural size 1.5-3 slabs were observed. They likely failed on the persistent weak layer.
Sunday
A size 2 persistent slab was remotely triggered in Allison Pass. Details here.
Saturday
A serious accident occurred on Thar Peak. 3 skiers were bootpacking up a couloir when they triggered a size 3 persistent slab. All were partially buried and sustained serious injuries. Another size 2 persistent slab was also remotely triggered nearby.
See photos for details.
Around 15 to 25 cm of new snow is expected at upper elevations by Wednesday afternoon, accompanied by strong southwesterly winds. Rain is possible below 1800 m.
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 60 cm deep across the region. This layer has been reactive in recent days.
The snowpack below is strong and well-bonded.
Tuesday Night
Cloudy. 10 to 15 mm of precipitation as snow or rain at treeline. 40 km/h southwest ridgetop wind. Treeline temperature -1 °C. Freezing level 1800 m.
Wednesday
Cloudy. 5 to 10 cm of snow. 30 km/h southwest ridgetop wind. Treeline temperature -2 °C. Freezing level 1800 m.
Thursday
Mix of sun and clouds. 0 to 3 cm of snow. 30 km/h northwest ridgetop wind. Treeline temperature -4 °C.
Friday
Mix of sun and clouds. 30 km/h northwest ridgetop wind. Treeline temperature -4 °C.
More details can be found in the Mountain Weather Forecast.
