Southeast Mountains

Recently formed slabs of drifted snow could remain sensitive to triggers where they formed over fragile weak layers.   Human-triggered and natural avalanche activity over the weekend tells the story.  Be cautious in leeward terrain where recently formed slabs are thicker and more cohesive, especially in higher consequence terrain.   Avalanche problems are smaller and less common at lower elevations.  

Yesterday's good visibility allowed us to better understand how our snowpack responded to the weekend storm.  As expected, the snow-favored Northwest Mountains saw a more widespread cycle, with many avalanches ranging from D1 to D2.5 in size.  The Southeast Mountains saw fewer avalanches, with sizes ranging from D1 to D2.  The largest avalanches in the snow-starved zone were right along the border of the two zones, and in long-running terrain such as Climax Chutes and Gothic.    Almost all of the avalanche activity broke in the new and drifted snow  - likely at the storm interface (our fragile January drought layer).   There were a few avalanches that appeared to pry out the thin, hard slabs that formed during mid January extreme wind event.  So far, we haven't documented any avalanches that broke deep into our early-season weak layers near the ground - let us know if you see one!  The pattern of fewer, smaller avalanches resulting from lower storm totals is why the Southeast Mountains are quicker to move to Moderate danger after the storm.  

Moving forward, we are re-categorizing the newly formed soft slabs into a new generation of persistent slabs.  Future instabilities in the recent snow should be limited to just the terrain where slabs formed over facets and faceted crusts.  Our pre-storm observations describe some of the characteristics of this January 23rd interface before it was buried (ex. Poverty Gulch, Baldy).  As the low-density snow from the weekend continues to settle into stiffer and more cohesive slabs in snow-favored areas, there may be increased potential for longer remote triggers or surprising slab behavior.  Of course, wind-loaded terrain has the thickest and most well-developed slabs.  The avalanche activity rose over the weekend helps demonstrate our most problematic terrain. We know that weak facets were well developed on west, north, and east aspects at all elevations, along with southeast aspects near and above treeline.  We have limited observations from high-elevation south- and southwest-facing slopes, and these slopes warrant similar caution given the wind loading patterns and a few notable avalanches on these aspects.