Use extra caution below ridge crests and rollovers. Wind slabs may not be bonded to the hard crust underneath.
Old wind slabs that were previously unreactive are starting to avalanche. This problem is most concerning in open terrain, where weak, sugary faceted crystals have formed under wind slabs, and on top of a thick crust.
Our North Rockies field team reported a small (size 1) rider triggered wind slab avalanche that likely occurred on Thursday or Friday on a northeast aspect in open, treeline terrain. See photos.
Looking forward to this weekend, it will continue to be possible for humans to trigger avalanches like this one.
If you head into the backcountry, consider posting to the mountain information network.
South through west aspects are stripped down to a thick crust that formed early in February. This crust exists at all elevations. On north through east aspects you will likely find old wind slabs over this crust. Due to recent cold temperatures, weak sugary snow crystals are forming under these wind slabs, which means they may be more likely to slide on the crust.
In treeline terrain that is sheltered from the wind, 5 to 10 cm of settled snow sits above the crust.
Surface hoar is growing on all aspects at all elevations up to 12 mm, even on ridgetops.
Friday Night
Clear. No new snow expected. Light to moderate south or southwest ridgetop wind. Freezing level valley bottom, with possible above freezing layer.
Saturday
Sunny. No new snow expected. Light to moderate south or southwest ridgetop wind. Freezing level rising to 1500 m plus possible above freezing layer.
Sunday
Partly cloudy. No new snow expected. Moderate southwest ridgetop wind, light on the east side of the forecast area. Freezing level valley bottom. Treeline temperature around -5 °C.
Monday
Partly cloudy. No new snow expected. Light to moderate southwest wind, with localised areas of strong wind. Freezing level rising as high as 1500 m on the east side of the forecast area.
More details can be found in the Mountain Weather Forecast.
