Avalanche Forecast

Southwest flow ushers in plenty of wind, moisture and a rising freezing level.

THURSDAY NIGHT: Freezing level at valley bottom, light to moderate southwest wind, 1 to 5 cm of snow possible.

FRIDAY: Overcast, freezing level at or near valley bottom, light to moderate west/southwest wind, 1 to 5 cm of snow possible during the day with another 1 to 5 cm possible Friday night.

SATURDAY: Overcast, freezing level beginning at valley bottom rising to about 900 m, moderate to strong southwest wind, 2 to 4 cm of snow possible during the day with 4 to 10 cm Saturday Night.  

SUNDAY: Overcast, freezing level beginning around 600 m climbing to about 1600 m during the day, strong to extreme southwest wind, 5 to 15 cm of snow at upper elevations with rain in the valleys.

In the neighbouring Cariboo region on Wednesday a surprisingly large human triggered avalanche was reported on a northwest facing feature at treeline. A similarly sized skier triggered avalanche was also reported near Revelstoke Wednesday on a steep west facing slope around 1600 m. These are great examples of the strange conditions created by reverse wind loading and may be a portent of things to come as the weekend trends warm and stormy.  

Previous to this, avalanche activity this week has been limited to small dry loose avalanches (size 1-1.5). In the adjacent Glacier National Park Region there were some large natural wind slab avalanches reported from extreme north facing terrain features on Monday.

The second week of February produced fewer persistent slab avalanches than the first week of February. But, the late January persistent weak layer is still showing signs of instability and warrants assessment. This MIN report from the Gorge is a helpful example of the lower elevation slopes where the surface hoar has been preserved. 

10 to as much as 20 centimetres of light density snow now rests on a variety of surfaces including sugary facets, feathery surface hoar, and wind-affected snow that formed as a result of the recent cold, dry and windy weather. 

Southwest wind is expected to increase as we head towards the weekend, it's difficult to pin down exact timing, but once it starts to blow touchy wind slabs are expected to form quickly and will likely be slow to heal as they rest on weak, sugary, faceted snow. Winds have varied in strength and direction over the past week, loading cornices and forming wind slabs at upper elevations. Watch for stiff wind slabs in unusual places as complicated cross-loading and reverse-loading patterns are prevalent. 

60-100 cm of snow from February is settling over a layer of surface hoar buried in late January. Reactivity on this layer has primarily been observed at treeline and in "treeline-like" features, like cutblocks, that are below treeline. On steep south-facing terrain, this layer may consist of facets on a sun crust, which has produced notable low probability/high consequence avalanches and requires a conservative approach. 

The mid/lower snowpack is generally well settled and strong.

• Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
• Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
• Extra caution is needed around cornices under the current conditions.