North Columbia

Be mindful of the persistent slab problem lingering at lower elevations as you search for snow that has been sheltered from recent winds.

High -

Friday night: Mainly clear. Light northeast winds.Saturday: Sunny. Light northeast winds. Alpine high temperatures around - 21.Sunday: Sunny. Light northeast winds. Alpine high temperatures around -16.Monday: Sunny. Light northeast winds. Alpine high temperatures around -13.

Reports from Thursday show a continuation of wind slabs reacting to ski cuts, with a trend toward smaller (size 1) releases. Larger and older buried wind slabs remain a concern for the weak faceted grains they sit above.On Wednesday, numerous rider triggered wind slab avalanches up to size 2 were reported primarily on northerly aspects at treeline and above. The largest one was a buried, hard wind slab that was sitting on facets on top of a crust. Expect these wind slabs to remain reactive to human triggers where they are sitting on facets.Over the past week there have been several reports of human triggered persistent slab avalanches. They have been large avalanches (size 2-2.5), occurring on a variety of aspects primarily below treeline. These have been failing on the persistent weak layer of surface hoar and/or crust that was buried mid January. This layer has created a low likelihood, high consequence scenario that requires discipline and careful terrain selection to manage effectively.

Recent strong northeasterly ridge-top winds have created wind slabs on lee features at treeline and above. Below this wind affected layer, older buried wind slabs exist on a variety of aspects. These remain a concern for overlying facets (weak, sugary snow), causing them to remain reactive for longer than is typical for a wind slab problem.There are two prominent weak layers in the upper snowpack. One was buried at the end of January, and the other mid-January. They are approximately 40- 60 cm and 60-80 cm below the surface, respectively. Both layers consist of surface hoar (weak, feathery crystals) and may be associated with a crust on steep, south facing slopes. These weak layers have been most reactive at lower elevations, and especially below treeline.The lower snowpack is generally considered to be strong, except for shallow, rocky areas where the cold temperatures continue to facet (weaken) the snowpack.