Avalanche Forecast

Moderate

We are coming out of a period of significant avalanche activity in the Purcells, with many notable large persistent slab avalanches. Buried weak layers have been very easily triggered with explosives, with several size 2 to 3 slabs reported on Tuesday, Wednesday, and Thursday. These avalanches have mostly been in alpine terrain and have propagated widely across terrain features. Over this period, humans testing smaller slopes have triggered several size 1 to 1.5 storm slabs in the top 40 cm of snow. There have also been some very large human triggered avalanches west of this region, where the weak layers are buried deeper.

Looking ahead to the weekend, triggering large persistent slab avalanches will remain a serious concern in this region.

Roughly 40 cm of recent snow has settled into a slab. This snow may contain a rain crust at elevations below 2000 m. The additional load of this recent snowfall has stressed multiple weak layers including:

• A facet and surface hoar layer directly beneath the recent snow

• 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)

All of these layers have shown signs of instability over the past few days and need more time to strengthen.

Friday night

Light snowfall with trace accumulations, 30 to 40 km/h wind from the southwest, treeline temperatures around -10 °C.

Saturday

Cloudy with very light snowfall, trace accumulations, 20 to 30 km/h wind from the west, treeline temperatures around -8 °C.

Mix of sun and cloud, no precipitation, 20 km/h wind from the northwest, treeline temperatures around -8 °C.

Mostly sunny, no precipitation, light wind, treeline temperatures around -10 °C.

More details can be found in the Mountain Weather Forecast.

• Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
• Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
• Remote triggering is a concern, watch out for adjacent and overhead slopes.
• Back off if you encounter whumpfing, hollow sounds, or shooting cracks.