Purcells

Human-triggered avalanches remain likely on weak layers buried deep in the snowpack. Avalanches occurring on these layers will be large with high consequences. Stay disciplined and make conservative terrain choices.

Explosive control initiated several large avalanches that released on the weak layers described in the snowpack summary.

Reports of new human-triggered avalanches have started to taper. However, with little change in the snowpack structure triggering large persistent slab avalanches remains a concern.

Human-triggered avalanches are still likely in alpine and treeline terrain, especially in steep, shallow rocky areas. This notable avalanche continues to provide evidence that these weak layers are with us for a while.

Increasing southwest winds throughout the day will likely start to build wind slabs in lee terrain features in the alpine and treeline. These wind slabs may further bury a surface hoar layer that has been forming over the past few days and is buried by a few centimeters of snow. The mid and lower snowpack consists of two buried weak layers, including:

• A surface hoar layer buried in mid-December that is 40 to 60 cm deep

• Weak faceted snow and decomposing crusts near the bottom of the snowpack, ranging from 70 to 150 cm deep.

Reports of new avalanches involving these layers have started to taper. However, little change in the snowpack structure means triggering large persistent slab avalanches remains a concern.

Thursday Night

Mostly cloudy, trace of new snow, 10 to 20 km/h southwest wind, treeline temperature -6 °C.

Friday

Mostly cloudy, flurries 1 to 3 cm new snow, 20 to 35 km/h southwest wind, treeline temperature -5 °C.

Partly cloudy, with trace amounts of snow. 20 to 30 km/h south wind, treeline temperatures -5 °C.

Mostly cloudy, 5 to 7 cm of new snow, 20 to 30 km/h southwest winds decreasing through the day, treeline temperatures - 5 °C.

More details can be found in the Mountain Weather Forecast.

• Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
• Choose conservative terrain and watch for clues of instability.
• Remote triggering is a concern, watch out for adjacent and overhead slopes.
• Back off if you encounter whumpfing, hollow sounds, or shooting cracks.