The warming we're moving into is the type of pattern that makes the Purcells thunder with avalanches. Time to back off from big, committing avalanche terrain and overhead hazards.
A trio of weak layers exist below the most recent storm snow and up to about 120 cm below the surface. They will be increasingly likely to produce avalanches with forecast warming. Small avalanches may also step down to the basal snowpack.
Warm temperatures and light rain will work to destabilize surface snow below 2000 m. Wet snow may shed naturally or with a human trigger.
Forecast warming is bringing the weak, faceted basal snowpack into question. As warming penetrates deeper into the snowpack, the chances of a full-depth avalanche increase.
A skier was partially buried in a size 1.5 avalanche in the Golden area on Tuesday. The slide ran on the late-January weak layer described in our snowpack summary. See the report HERE. A slew of natural avalanches were seen elsewhere in the Dogtooth Range. Activity of this type is expected to resume or even intensify as forecast warming tests the snowpack.
Natural activity during the recent storm involved storm snow and buried weak layers, which produced avalanches to size 3.
By Thursday, a new melt-freeze crust should glaze the surface on solar aspects and below about 1900 m. The depth of affected snow should increase over the coming days, but crust recovery may be weak. This process will affect 20 to 45 cm of settling recent snow, which has been affected by strong southwest winds at treeline and above. In shelter, it sits over a surface hoar or crust layer from mid-February.
Two more weak layers exist: a layer of facets, surface hoar, or crust from late-Jan buried 30 to 50 cm deep, and a layer of facets from early Dec, buried 70 to 120 cm deep. In many areas, facets or depth hoar also exist at the base of the snowpack. All of these layers are a concern as forecast warming tests the snowpack.
Wednesday Night
Clear skies. 10 to 15 km/h west ridgetop wind, up to 60 km/h in high alpine, increasing. Treeline temperature 0 °C. Freezing level rising to 2000 m.
Thursday
Partly cloudy with a chance of light rain. 15 to 30 km/h southwest ridgetop wind, up to 70 km/h in high alpine. Treeline temperature 3 °C. Freezing level rising to 2300 m.
Friday
Mostly sunny. 10 km/h southwest ridgetop wind. Treeline temperature +5 °C. Freezing level rising to 2400 m.
Saturday
Sunny. 5 to 10 km/h southwest ridgetop wind. Treeline temperature 4 °C. Freezing level 2500 m.
More details can be found in the Mountain Weather Forecast.
