A steady stream of snowfall has been trickling into our area since mid-February, and the weight is piling up. Skiing and riding conditions have been fantastic, but the weak layers in our snowpack are struggling to carry this additional load. A stronger pulse of moisture last weekend pushed the snowpack to its breaking point, producing a significant natural avalanche cycle. A spate of human-triggered avalanches during and after this storm resulted in some close calls, though no serious accidents have been reported.

So, what’s going on with the snowpack and why are there so many avalanches visible in the mountains above the Wood River Valley? Right now, we are deal-ing with what are known as persistent slab avalanches. The weak layers involved in these types of slides tend to behave in unpredictable ways and to stick around for a long time.

An extended period of cold temperatures combined with alternating droughts and minor storms dominated the weather in January and early February. This weather produced widespread weak layers at the surface of the snowpack. Weak stacks of facets that resemble early-season weak layers can be found on shaded slopes, while facets paired with crusts found on slopes that face the sun. These layers started to be buried in mid-February when consistent snowfall returned to the region, planting the seed for our persistent slab problem.