Welcome back to backcountry zone summaries for the 2017-18 season! This season's snowpack began building after snow fell in early October snowfall. Shallow snow so early in the season creates the potential for lingering Persistent Slab avalanche problems. That prompted us to write a blog discussing our potential paths going forward, and none of them looked great for snow stability. Unfortunately, it looks like the poor snowpack structure came to fruition and may linger well into the season.
The snow that fell in October and didn't melt off has gradually metamorphosed into weak basal facets and crust-facet combinations. In the Grand Mesa zone, these trouble spots are limited to high, cold slopes (generally those facing northwest through north to east), so this worrisome layer of basal facets isn't widespread. The Grand Mesa zone didn't receive much snow from Friday's storm, but in other zones it was enough to test of the weak foundation. It did not hold up well. Anywhere the new storm snow fell on a preexisting snowpack, we saw evidence of instability: avalanches, shooting cracks, and propagating snowpack tests. Expect similar conditions in the limited areas where the Grand Mesa received eight inches or more of recent and drifted snow.
That means the most dangerous slopes are also the most attractive for recreating. We're going to be lured to slopes with deeper coverage. Despite all the rocks, shrubs, and bare ground poking through the thin snow coverage in most places, it is avalanche season up high.
Be cautious near, on, or below, any slope steeper than about 30 degrees that looks like rocks and shrubs are buried and no longer visible. This near miss in the adjacent Aspen zone is exactly the type of event we want to avoid. You can trigger avalanches from below or from a distance. Give yourself a wide buffer around potential avalanche terrain to account for this unpredictability. The Persistent Slab avalanche problem will be with us for a while.
On other slopes, you're biggest risk it hitting shallowly buried obstacles. It's still early, don't blow your whole season getting injured nailing something.