The first deep persistent slabs of the warmup have been reported and there are likely many more to come. Time to dial down your exposure to avalanche terrain and overhead hazards to a minimum.
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.
Solar warming will work to destabilize snow on sun-exposed slopes sheltered from wind. Wet snow may shed naturally or with a human trigger. Loose snow releases may trigger destructive slab avalanches.
Forecast warming is bringing the weak, faceted basal snowpack into question. As warming penetrates deeper into the snowpack, the chances of full-depth avalanches increase.
Two size 3 deep persistent slabs and one size 2 were targeted with explosives near the Bugaboos Wednesday, evidence of the basal snowpack reacting to large triggers. The same mission produced shallower persistent slabs on the late-January crust, the layer that partially buried a skier in a size 1.5 in Golden on Tuesday and produced natural size 3 and 3.5 releases in the Dogtooth Range Wednesday. Activity of this type should resume or even intensify as warming continues.
A melt-freeze crust moist or snow now glazes the surface on solar aspects and, by Friday, 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 warming tests the snowpack.
Thursday Night
Cloudy. 5 to 20 km/h west ridgetop wind, easing. Freezing level remaining near 1700 m.
Friday
A mix of sun and cloud. 0 to 5 km/h southwest ridgetop wind. Treeline temperature 4 °C. Freezing level to 2300 m.
Saturday
Mainly sunny. 5 to 10 km/h southwest ridgetop wind. Treeline temperature 4 °C. Freezing level 2500 m.
Sunday
Sunny. 0 to 5 km/h south west ridgetop wind. Treeline temperature 4 °C. Freezing level 2300 m - 2700 m.
More details can be found in the Mountain Weather Forecast.
