Kootenay Boundary

Approach terrain with a conservative mindset, and continually gather information. The avalanche danger is improving, but the snowpack is complex. Patience and diligence are required to make safe decisions.

Tuesday Night: Cloud clearing. Possible trace of snow expected. Light to moderate northwest wind. Strong at higher elevations. Freezing levels fall to valley bottom. Temperature inversion keeping alpine temps around -5 C.

Wednesday: Scattered cloud, possibly clear by the afternoon. No new snow expected. Moderate northwest wind trending to extreme at higher elevations. Freezing levels at valley bottom overnight, and rising to 750 m through the day. Alpine high around -6 C.

Thursday: Mostly sunny. No new snow expected. Light southwest wind trending to moderate northwest at higher elevations. Freezing levels at valley bottom overnight, and rising to 600 m through the day. 

Friday: Mostly sunny. No new snow expected. Light southwest wind trending to strong at higher elevations. Freezing levels at valley bottom overnight, and rising to 600 m through the day. 

A few thin crust and/or surface hoar layers in the upper snowpack have been producing isolated sudden results in snowpack tests. While this is not a cause for widespread concern, it is worth gathering some extra snowpack information before committing to a feature. 

On Sunday, a large natural avalanche was reported in the backcountry near Whitewater. After talking to some professionals in the area, it sounds like it occurred late last week during the storm. There is a great picture in this Mountain Information Network post. It was a wide propagation, and it looks like it started mid-slope on a sparsely treed ridge. There was a similar avalanche on the same feature in a previous storm, so this may be a new slide on a reloaded bed surface.

There are reports of a surface crust on steep solar aspects from the recent warm temperatures and sun, 1-10 cm thick. Surface hoar growth is widespread in terrain that hasn't seen recent wind, mostly 5-10 mm, and up to 25 mm. The thickest crusts and largest surface hoar have been reported around Whitewater ski resort. 

A series of recent surface hoar layers and melt-freeze crusts can be found in the top 50 cm of the snowpack, up to 2400 m. The crusts are thicker on southerly aspects. These layers have not been resulting in recent avalanches and have not produced concerning results in snowpack tests yet. 

A strong, well-consolidated mid-pack exists below this and above the early December crust/facet interface. 

The early December crust/facet layer has been responsible for sporadic but very large, persistent slab avalanches over the past month. The crust is now buried 120-200 cm deep except in thin, wind-affected areas near ridgetops. Daytime warming, sun, cornice fall, and smaller avalanches through the forecast period may be enough to wake this layer up and initiate large to very large avalanches.

• In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
• If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.
• Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
• Avoid terrain traps where the consequence of any avalanche could be serious.