Avoid avalanche terrain during time of rapidly rising freezing levels.
Unseasonably warm weather will trigger large and very avalanches over the next few days.
The likelihood of persistent slab avalanches will increase with each day of warm weather. Uncertainty remains about how the persistent weak layer will react to the rapid warming.
Intense warming will likely trigger numerous loose wet avalanches. These may step down to deeper layers resulting in larger-than-expected avalanches.
On Tuesday, large persistent slab and wind slab avalanches (up to size 2.5) occurred naturally on east slopes at treeline and alpine, respectively. Whumpfs and shooting cracks were also observed at treeline and below. Over the last week, skiers were surprised by large avalanches; several were remotely triggered from a distance from low-angle or flat terrain. Expect increasing avalanche activity with the incoming warm weather.
Expect to find up to 20 cm of settled snow in wind-sheltered and shady areas. This snow covers wind-affected surfaces or a hard crust at upper elevations. The wind has scoured down west alpine slopes to a crust. A layer of weak, faceted crystals over a crust, or surface hoar, is the primary layer of concern, buried around 40 to 80 cm. This layer has been reactive, especially at treeline and below, over the last week.
A sun crust has formed on the surface on steep south and west-facing slopes, and snow is heavier and moist at lower elevations.
Thursday Night
Cloudy with 2 to 4 cm of new snow expected. 50 to 60 km/h southwest ridgetop wind. Treeline temperatures around 0 °C. Freezing level around 1500 m.
Friday
Mainly cloudy with no precipitation, 30 to 40 km/h southwest ridgetop wind. Treeline temperatures around +6 °C. Freezing level rising to 2500 m.
Saturday
Cloudy and sunny periods with no precipitation. 25 to 35 km/h southwest ridgetop wind. Treeline temperatures around +8 °C. Freezing level rising to 3000 m.
Sunday
Mix of sun and clouds with no precipitation, 40 to 50 km/h southwest ridgetop wind. Treeline temperatures around +6 °C. Freezing level around 2500 m.
More details can be found in the Mountain Weather Forecast.
