Southeast Mountains

Recent skier and remote-triggered avalanches over the past two days (Marble yesterday; Schuylkill Ridge, Pearl Mtn, Marble on Sunday) highlight the potential to trigger slabs 1 to 2 feet thick over faceted weak layers near and above treeline. Watch for cracking and collapsing, dig down a couple of feet, and use visual clues to identify slopes with recent slab development. Carefully consider terrain consequences before committing to steep slopes where slabs are present. The safest travel is below treeline or on wind-eroded terrain.

Avalanche danger is gradually trending downward after Sunday’s storm, but the most problematic terrain remains unchanged.  The pattern of recent natural avalanche activity shows the leeward aspects (northeast to southeast) above 11,000' have been most active.   We’ve seen numerous skier-triggered avalanches on northeast aspects near treeline—this appears to be the bullseye for the most sensitive and widespread problem.   Terrain like Schuylkill Ridge or Mt. Axtell held very thin, weak snow through the December drought and received just enough snow last week to form a soft, sensitive slab (see video from Schuylkill Ridge). 

We pulled wind slabs off the problem list today because they're expected to be unreactive where they formed over non-persistent weak layers.  However, we expanded the persistent slab rose to include wind-loaded southerly aspects.  Our targeted fieldwork yesterday suggests that small-grained facets have formed above some of the thick crusts that are pervasive across the south side of the compass. This weak layer formed quickly due to strong temperature gradients associated with warm crusts buried by colder snow (see melt-layer recrystallization), and wasn’t something we could track during the dry spell. As a result, we have more uncertainty about its distribution and sensitivity compared to the bullseye data we have from the shadier aspects.  A dose of caution and careful snowpack assessments are warranted if you're traveling on steep southerlies at higher elevations.       

Yesterday's forecast discussion went into detail about the tricky distribution of our buried facets. Fragile and problematic on some slopes, absent on the next.  Now we're complicating the equation with another potential weak layer.  When weak layer distribution is in question, it's often easier to focus on the presence or absence of a slab.  Slabs are still poorly developed, often localized to just leeward features, or in some sheltered areas as you gain elevation in snow-favored areas.  Monitoring slab development and evaluating terrain consequences if one releases are key strategies for safely stepping into more complex avalanche terrain right now.