Avalanche Forecast

Moderate - We have a good understanding of the snowpack structure and confidence in the weather forecast Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

WEDNESDAY NIGHT: Clouds clearing through the night. Light rain expected, possibly heavier on the far east end of the region. Moderate southwest ridgetop wind trending to northwest by the morning. Freezing level falling to around 1300 m.

THURSDAY: Sunny with scattered clouds in the afternoon. No new snow expected. Ridgetop wind decreasing to light from the northwest. Freezing level rising to around 1700 m.

FRIDAY: Partly cloudy. No new snow expected. Light southwest ridgetop winds. Freezing level around 2100 m.

SATURDAY: Mostly cloudy. No new snow expected. Light south ridgetop wind. Freezing level around 2200 m. 

On Tuesday and Wednesday, widespread, loose wet avalanches were reported due to warm temperatures and/or sunshine (size 1-2). 

A few natural and human-triggered wind slabs occurred in the alpine and treeline on Monday (size 1-2). 

There have been some notable human-triggered avalanches in Kootenay Pass and the Nelson area in the past week. These large slab avalanches (size 2), failed on either a buried sun crust on solar aspects or surface hoar on shaded aspects. This MIN report from an incident on Saturday near Whitewater is an example of this problem. 

On Friday, an operator south of Nelson reported a large slab avalanche (size 3), triggered by a helicopter landing initiating a cornice failure. This avalanche stepped down to a deeper weak layer in the upper snowpack, suggesting that these deeper layers are still possible to trigger with large loads.

50 to 70 cm of settling storm snow exists at higher elevations. New snow depths taper significantly with elevation, with moist and crusty surfaces below 2000 m and on south aspects into the alpine. 

Last week's storm snow is bonding poorly to underlying layers in some areas. In the Selkirks, especially north of Nelson, it appears that this snow is bonding poorly to the underlying sun crusts on solar aspects and surface hoar on shaded aspects. In the Monashees, reports suggest that this snow has formed a stronger bond to underlying crusts. Several other crust/facet layers exist in the upper 100 cm of the snowpack. Human-triggered avalanches on these layers are unlikely, but large triggers such as a cornice failure, or a smaller avalanche stepping down to these layers is possible.

• If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.
• Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
• Be aware of the potential for large avalanches due to the presence of a persistent slab.
• Be alert to conditions that change with aspect and elevation.
• When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
• Avoid steep slopes when air temperatures are warm, it is raining, or solar radiation is strong.