North Rockies

New snow and wind will continue to build fresh and reactive wind slabs. If triggered, wind slabs have potential to step down to a deeper weak layer.

Moderate

• Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
• Uncertainty is due to the limited number of field observations.

On Saturday this MIN report from Bullmoose described fresh wind slab development, whumphing, reactive cornices and evidence of a widespread natural wind slab avalanche cycle suspected to have run sometime midweek.

If you head into the backcountry, consider sharing your observations with the Mountain Information Network.

As small amounts of new snow arrive with wind, wind slabs continue to build in leeward alpine and treeline terrain.

A crust from mid December, surrounded by weak facets, is buried 50 to 170 cm deep, depending on aspect and wind loading. Over a week ago, a large natural avalanche cycle ran on this layer.

In thin snowpack areas, faceted grains or depth hoar may exist at the base of the snowpack. Snowpack depths are well above average for this time of year, around 2 m at treeline.

Sunday Night
Mostly cloudy. 5 to 10 cm of snow. 70 km/h southwest ridgetop wind. Treeline temperature -1 °C. Freezing level 1600 m.

Monday
Mostly cloudy. 5 to 8 cm of snow. 80 km/h southwest ridgetop wind. Treeline temperature -1 °C. Freezing level 1600 m.

Tuesday
Mostly cloudy. 60 km/h west ridgetop wind. Treeline temperature 1 °C. Freezing level 1900 m.

Wednesday
Mix of sun and clouds. 80 km/h southwest ridgetop wind. Treeline temperature 2 °C. Freezing level 2400 m.

More details can be found in the Mountain Weather Forecast.

• Watch for newly formed and reactive wind slabs as you transition into wind-affected terrain.
• Avoid steep, rocky, and wind-affected areas where triggering slabs is more likely.
• If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.