Southeast Mountains

Natural avalanche activity should be winding down now, but conditions remain dangerous because human triggering is still likely today.  Weak layers buried up to several feet thick are showing minimal signs of improvement - every observation from this weekend has highlighted collapsing snow or remotely triggered slides.  There have been 3 avalanche fatalities and numerous close calls since Friday around Colorado; one of which was in our backyard.   Steep terrain that faces west through north through east is most dangerous.  You can easily trigger avalanches while traveling on or from below terrain like this.  Conservative terrain selection and careful snowpack assessments are paramount today.  

Our observations page reads like a horror story right now.  Take the time to read through the dozens of observations of naturals, human and remotely triggered slides, collapses, and shooting cracks.   While the slides in the alpine on Richmond and Yule Pass are scary large, the dozens of smaller slides in below treeline terrain like Snodgrass or Coney's should also catch your attention.  Avalanche activity below treeline has been more widespread and large enough to be dangerous, especially around terrain traps.   The wind loading has ended and we are a few days out from the last snowfall event, so the danger will start to gradually trend down until our next storm on Tuesday afternoon.  Allow me to emphasize the word gradually.  Natural avalanche activity will be unlikely today, but these weak layers have refused to quiet down for human triggers.  Persistent slabs are still reactive to the weight of skiers and riders.  They'll be a little harder to trigger at higher elevations because the slabs are denser and thicker, yet the triggered slides will also be larger.

Thanks to everyone's observations from the past week, we have compiled an impressive record of avalanche activity since our fragile weak layers were buried on December 10th.  Let's dive into that data a little now, which I have included in the first image of our media gallery below.  This discussion will add more detail and insight into our current persistent slab distribution rose.   Since our snowy period began on December 10th, we've recorded 254 avalanches.  Almost half of these were from below treeline slopes, where the persistent weak layer is weakest thanks to our strong inversions in early December when it was forming.    You'll notice that all of the activity below treeline was on west through north through east aspects.  That's where there was existing faceted snow coverage prior to the storms.  Northeasterly aspects are the epicenter of activity.  That's in part, because those slopes held the weakest of the weak layers: they were the most protected from the sun and from the wind back when the weak layers were forming.  There's also a strong data bias here because our valley's geography is such that most of our avalanche terrain on shaded aspects faces northeast (think Snodgrass, Coneys, Schulkill Ridge, Happy Chutes, etc).  I wouldn't read into the lack of avalanche activity below treeline on northwest aspects: we simply don't have many northwest facing slopes that we can access or see easily.  At higher elevations, northwest aspects have been getting scoured by numerous northwest wind events, so finding a slope holding persistent slab structure is less common. We've kept it on the rose for simplicity's sake.  The 12/10 weak layer wasn't quite as weak above treeline, thanks to various wind effects and wind crusts capping it before burial.  While there have been fewer slides above treeline, you'll notice the destructive sizes are generally larger.  That means it may not be as easy to trigger an avalanche in the alpine, but if you do, it will be larger.  The final and most important point is the lack of avalanche activity on southerly aspects. South facing terrain was either dirt or thick crusts prior to our storms, so there aren't persistent weak layers below the recent snow.  As you wrap further away from due south, the buried crusts get thinner and more collapsible.  We've seen a few slides on SW and SE aspects above treeline which may have been from these crusts collapsing, or which may have simply been wind slabs on non-persistent weak layers.  Either way, our snowpack assessments suggest that as you move away from due south towards SE to ESE aspects or to WSW aspects, the persistent slab structure becomes evident again on steep terrain.  If you're hunting out steeper terrain on the southern quadrant of the compass, the more due south-facing, the better,  and be mindful of smaller wind slabs that formed over the weekend.