Avalanche Forecast

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. On Sunday, the Kooteney Boundary will see more significant snowfall levels and on Monday heavy snow is forecast.

FRIDAY NIGHT - Snow with 5-15cm accumulation, light southwest ridgetop winds gusting strong, alpine high temperature -4C & freezing levels near 1200m.

SATURDAY - Mainly cloudy then increasing snow in the afternoon with accumulations of 20-30cm, ight southwest ridgetop wind gusting strong, alpine high temperature -3C & freezing levels 1400m.

SUNDAY - Mainly cloudy then increasing snow in the afternoon with accumulations of 5-10cm, light southwest ridgetop wind gusting strong, alpine high temperature +1C & low temperatures -3C & freezing levels rising to near 2000m.

MONDAY - Heavy snow with accumulations of up to 50cm, light southwest ridgetop wind gusting strong, alpine high temperature +1C & low temperatures -1C & freezing levels rising to near 2000m.

There has been widespread human triggered avalanches reported in the past 2-3 days. On Friday a few notable small to large (size 1.5-2) avalanches were reported and included a few "surprises". One was reported as a remote avalanche and the other was a large skier accidental. Both avalanches appear to have run on that the surface hoar layer and were in north, northwest or west aspects between 1850-2050m.   

As snow fall continues to bury these layers increases we expect to see fewer obvious clues though the size of potential avalanches increase. In other words, as these layers are more deeply buried, they may be harder to trigger, but the resultant avalanches will be far more destructive. Classic trigger spots of deep layers are in "thin-to-fat" snowpacks around ridges or while transitioning into bowls.

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 Hummingbird pass reports shooting cracks and whumpfing, easy snow pit results, and evidence of recent avalanches. 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.    

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!

Another 10-15cm overnight Friday will add to recent snow fall amounts of 15-30cm for a total of 30-45cm of snow in the past 72 hours and 40-75cm in the past week. At upper elevations, moderate to strong southwest wind has likely blowing the new snow into fresh slabs that may be reactive to human triggers.

As of Saturday morning 2 known weak layers will be buried 40-75cm: a rain crust from the first week of December and a surface hoar layer that formed in clear weather soon after. Both have shown significant and widespread signs of instability in recent days.  

Numerous MIN's from Thursday report ongoing signs of instability on both of these weak layers, many of them with avalanches to report so they are shared in the avalanche summary. This MIN from the Whitewater backcountry on Thursday found ongoing signs of instability and test pits showed "easy pop" results down 45cm.The depth of these weak layers is less in the Rossland as indicated by this MIN.  

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.

• Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
• 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.
• Avoid steep convex slopes.