Southeast Mountains

Carefully assess the snowpack before riding on slopes steeper than 30 degrees.  On the northern half of the compass, it is possible to trigger a large avalanche that breaks several feet thick on weak layers near the ground.  Recently wind-loaded terrain is most suspect.  Collapses and shooting cracks are signs of unstable snow.  The safest riding is on southerly aspects or on slopes that avalanched last week.  

Our last reported persistent slab avalanche was skier triggered on December 12th, yet our observations page has been a steady stream of collapses and shooting cracks all week, a clear sign of unstable snow.    The early season weak layers that were buried by our big December storm continue to warn us of their presence on the northern half of the compass.  Evidence from field observations this week suggests that the most reactive persistent slabs are below treeline, especially in the Southeast Mountains.   That's where slabs are thinner and the weak layer smorgasbord (surface hoar, depth hoar, and facet layers) are most fragile.  On the upside, we have also observed the most extensive natural activity below treeline, and the problem appears to be fairly isolated at lower elevations in steep terrain.  This means that there are a lot of steep slopes below treeline where you can ride without encountering the problem, but if you stumble upon a lingering pocket with the entire season's snowpack, it will still be fairly easy to trigger.  And given that you'll probably be riding in sparse glades, the resulting avalanche could drag you into trees.  This video highlights some strategies for reducing your risk if you are traveling on shady aspects in the trees. 

Near and above treeline, we've observed the persistent slab problem trend to stubborn.  That's because slabs are thicker and denser, making it harder to impact weak layers, and because weak layers aren't quite as fragile, in general, so the snowpack is adjusting.  This is a tricky setup.  It means that you and your partners could cross an unstable slope without any feedback.  Or you hit the sweet spot - often a shallow area on the margin of the slab - and bring down a large, potentially wide avalanche. This avalanche triggered yesterday in Summit County is a great example, as is this one from the San Juans, that was remotely triggered from almost a quarter mile away earlier this week.   The snowpack is more variable above treeline and harder to assess.  Here are few strategies if you want to take advantage of the nice weather to travel in the alpine.  1) Choose routes on southerly aspects, where weak layers don't exist at the bottom of the snowpack.  If you are accepting greater risk and traveling on the northern half of the compass, then 2) Choose smaller terrain features with cleaner runouts, devoid of gullies.  And 3) Avoid slopes where the recent wind loading has further stressed the snowpack, primarily on the northeast quadrant.  You can feel more confident traveling in steep terrain where slabs were eroded by the extreme wind event last week.