Avalanche Forecast

High - Confidence is due to a stable weather pattern with little change expected. The snowpack structure is generally well understood.

Monday Night: Mostly clear. No new snow expected. Generally light west wind, periods of moderate northwest at higher elevations. Freezing level dropping to valley bottom, Alpine low around -3 C.

Tuesday: A mix of sun and cloud. Possible trace of snow expected. Light southwest wind trending to moderate northwest at higher elevations. Freezing levels rising to 700 m through the day. Alpine high around -3 C.

Wednesday: Partly cloudy, 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 500 m through the day. 

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 400 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.

On Saturday, there were several reports of snowballing/pinwheeling/point-releases, a few small cornice failures, and small, loose-wet avalanches on steep solar aspects. 

On Friday, several natural wind slab avalanches were reported in Kootenay Pass. They were mostly on northeast aspects at treeline.

There are reports of a surface crust on steep solar aspects from the warm temperatures and sun on Saturday and Sunday, and surface hoar up to 10 mm growing in sheltered areas.

10-20 cm of recent snow combined with strong winds formed wind slabs and buried a series of recent surface hoar layers and melt-freeze crusts found down 15 cm and another down 25 cm. These extend to 2400 m and are most prevalent (thicker) on southerly aspects. 

Digging deeper, down 50-60 cm is yet another surface hoar layer that has seen recent avalanche activity. A 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.

• Avoid terrain traps where the consequence of any avalanche could be serious.
• 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.