Kootenay Boundary

Buried weak layers lurk are showing reactivity. As more snow falls, avalanche size will increase. Avoid steep, complex or convex slopes & choose conservative terrain. Human triggered and remote avalanches are likely. Back off if you see any signs of instability?

Stormy weather continues through the weekend bringing waves of precipitation and moderate to strong ridgetop winds. Incremental 5's and 10cm's of snow will add up. Then on Sunday, the Kooteney Boundary will see big snowfall levels.

THURSDAY NIGHT - Cloudy with isolated flurries with trace to 5cm new snow, 15-30km/h ridgetop west wind, alpine hlow temperature -7C & freezing levels 900m.

FRIDAY - Snow increasing throughout the day with 10-20cm new snow, southwest ridgetop winds 25-65 km/h, alpine high temperature -5C & freezing levels near 1100m.

SATURDAY - Mainly cloudy then increasing snow in the afternoon with accumulations of 10-20cm, southwest wind 25km/h gusting to 70 km/h, alpine high temperature -4C & low temperatures near -4C & freezing levels 1300m.

SUNDAY - Snow with accumulations of 15-30cm, southwest wind 20km/h gusting to 80 km/h, alpine high temperature 0C & low temperatures -5C & freezing levels rising to near 1800m.

As snow fall amounts increase we expect to see the size of avalanches increase. Weak layers continue to show signs that new snow is not bonding well. Recent avalanches and signs of instability were reported on a buried rain crusts, which is especially thick on southern aspects and a buried surface hoar layer, which appears to be especially preserved on northern aspects.  

On Thursday there were ongoing reports of human triggered avalanches (intentional ski cuts) to size 1.5 that were running on both weak layers of interest (the crust and the surface hoar layer). This reactivity was reported on northern aspects at around 2000-2100m. This MIN from the Whitewater backcountry on Thursday found ongoing signs of instability and test pits showed "easy pop" results down 45cm. This MIN from farther south found touchy conditions with "electric propagation" on ski cutting. They were able to intentionally trigger small avalanches easily in steep unsupported terrain. Both teams share the same advice: avoid steep, exposed or complex terrain.  

This MIN from Kootney Pass on Wednesday reports "touchy" conditions on lee (E) aspect at treeline with 20-25cm over the known weak layers.  

On Tuesday, there were numerous reports of widespread natural and skier triggered small avalanches to size 1.5. A skier accidental avalanche was also reported to have failed on surface hoar that was buried up to 20cm deep. Other reports were of skier remote avalanches occurring from 40m away on the same buried surface hoar layers.  

Please submit your observations to the Mountain Information Network (MIN). Photos are especially helpful! Thank you so much for all the great MINs submitted so far!

Recent and forecast new snow will incrementally loading weak interfaces. A total of 10-20cm fell overnight Wednesday in addition to the forecast 5-10 for Thursday. This adds up to a total of 40-60cm over known weak layers by Friday morning. More snow is forecast to fall late in the day Friday and overnight into Saturday.  

The two layers we are tracking are a rain crust from the first week of December and a surface hoar layer that formed in clear weather soon after. Both have shown signs of instability in recent days.  

As of Wednesday 25-30cm were over the weak layers as reported in this MIN's from Kootenay pass area. This MIN from an AST-2 course also reported signs of instability on this crust. This MiN reports some reactivity to skier traffic in wind affected area.  

At upper elevations, moderate to strong southwest wind has likely blowing the new snow into fresh slabs that may be reactive to human triggers.

Snowpack depths vary with elevation, treeline averages between 50-100 cm. 

The early November crust is sitting about 10-30 cm up from the ground. There is a late November crust in the midpack in some places as well. Uncertainty with these crusts exists due to limited observations, but there haven't been any recent avalanches reported on these layers in this region.

• Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
• Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
• Keep in mind the crust offers an excellent bed surface for avalanches.
• Avoid steep convex slopes.