Purcells

Approach terrain with a conservative mindset, and continually gather information. Tricky, deep persistent slab problems are still on our minds. Patience and diligence are required to make safe decisions.

Wednesday Night: Mostly clear. No new snow expected. Light north wind, alpine winds tapering off to light from extreme northwest. Freezing level at valley bottom. Alpine low around -7.

Thursday: Mostly sunny. No new snow expected. Light southwest wind trending to strong northwest at higher elevations. Freezing level at valley bottom overnight, rising to 500 m by the afternoon. Possible temperature inversion brings alpine highs to around -3 C.

Friday: Mostly sunny. No new snow expected. Light southwest wind trending to extreme west at higher elevations. Freezing level at valley bottom overnight, rising to 700 m by the afternoon. Possible temperature inversion.

Saturday: Mostly sunny. No new snow expected. Light southwest wind trending to strong west at higher elevations. Freezing level at valley bottom overnight, rising to 700 m by the afternoon. Temperature inversion breaking down.

No new avalanches were reported by 4 pm on Wednesday.

On Tuesday, a professional operation south of Golden reported a few cornice falls that triggered size 2 slab avalanches on the slopes below. These occurred in steep terrain at treeline and above. 

On Monday, professional operations in the north half of the region reported numerous natural windslab avalanches, mostly size 2 to 2.5, with one size 3 reported. These wind slabs were mostly in steep, alpine terrain, and were presumed to be the result of loading from moderate to strong northwest to southwest winds.  

On Saturday, west of Invermere, a small, rider triggered avalanche was reported to have failed on the early December persistent weak layer. The snowpack may be shallower in this location, making this layer easier to trigger, but it's a good reminder that this crust/facet combo has not healed. 

New surface hoar is growing on top of 2- 5 cm of fresh snow that fell overnight between Monday and Tuesday. This covers another layer of surface hoar up to 12 mm in sheltered terrain, and a crust on solar aspects. This crust is reported to be thicker (up to 2 cm) and more likely to be present on steep slopes. 

In the northern end of the region, the upper snowpack seems to be mostly wind effected, especially in the alpine. 

This Mountain Information Network post seems to indicate that the surface crust could be thicker and more solid in the south end of the region. 

A couple of thin surface hoar and crust layers exist in the upper 40 cm of the snowpack. These layers have not been producing concerning results in recent snowpack tests.

The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 90-160 cm. This layer was reactive last week producing large size 3 avalanches.

Activity has tapered, however, daytime warming, sun, cornice fall, and human triggers from steep, rocky slopes, with a shallow or thin-to-thick snowpack may still be able to trigger this weak layer. 

• In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
• Start on smaller terrain features and gather information before committing to bigger terrain.
• Use caution above cliffs and terrain traps where even small avalanches may have severe consequences.
• Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.