Northwest Mountains

It remains possible to trigger a soft slab in this week's snow where deeper accumulations or drifts formed over facets, most commonly near and above treeline.  Recent human-triggered slides exemplify the problem, including one close call/ remote trigger near Marble.  Slabs are largest and most dangerous on wind-loaded slopes at high elevations - the safest riding is at lower elevations where slabs are thinner and more isolated. 

Now that a few days have passed since Tuesday's storm, most wind and storm slabs have healed.  However, instabilities involving the recent snow could linger where well-developed slabs formed over a layer of thin facets above the meltdown crust.   These facets formed from melt-layer recrystallization - a process that requires a specific set of ingredients that weren't widespread at the start of this week's snowfall.   In other words, the layer is spotty in distribution. We have found it on various aspects around the compass (ex. Baxter Basin and Elkton) and have also found it absent on those same aspects.  We have lower confidence describing where the layer is most likely to be found, but higher confidence describing where in the terrain slabs above this layer have formed.    In the Ruby Range, storm totals this week exceed 2" of Snow Water Equivalent, and slabs are fairly ubiquitous around the compass as you gain elevation into higher terrain.  As you move away from the favored Snowbelt, slabs have only formed on well-drifted slopes favored by westerly winds.  Carefully assess for the presence/absence of a slab and how the slab is bonding before riding in steep, consequential terrain.

High northerlies are the only slopes that didn't see extensive meltwater into the snowpack last week. On these coldest aspects, a more winter-like snowpack structure exists. This requires consideration for weak layers near the ground that have plagued us this winter, especially on terrain with unusually shallow snow depths. The most recent human-triggered examples of the problem include a snowmobile-triggered slide on Axtell and a skier-triggered slide on Gothic.   In the San Juans on Wednesday, a skier was surprised when they triggered a shallow wind slab that stepped down and produced a very large avalanche. 

It's that time of year when it doesn't take much sunshine to cause shallow wet loose avalanches in fresh snow.  Today's increasing clouds should hopefully limit the issue; the threat of wet loose avalanches involving the new snow will increase tomorrow and later in the week as the sun returns in full force and temperatures warm.  The instability is easy to recognize. Look for rollerballs, pinwheels, and natural sluffs as the snow surface gets damp.  

Events: CBAC's Party for the People is at the Talk of the Town next Thursday.  Come celebrate the end of the season with us!  (Don't worry, we'll be forecasting for at least a few more weeks.)