Boletín de aludes

Northern New Mexico

Taos Avalanche Center
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Peligro de aludes

Sat
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 6 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Triggering a persistent slab avalanche on West through North to East aspects is possible today. Slopes greater than 35 degrees, especially ones that have seen deposition or stiffening from the wind, should definitely be on your radar. Audible collapses and shooting cracks have been a reliable source of immediate feedback that you've found this instability. A persistent slab avalanche, if triggered, has the potential to be large and capable of burying a skier or rider. Sticking to lower angle wind sheltered terrain will help to manage much of the avalanche problem today.

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Cohesive slabs formed from recent storms and wind deposition are resting on top of weak faceted snow. These slabs are generally soft and 1 to 2 feet thick. Areas that have seen the most wind will have thicker, stiffer slabs. There are two main layers of concern to look out for. One is a layer of basal facets/depth hoar that rests near the ground. We have seen failures on this layer in areas with the shallowest snowpack. The second is a layer of near surface facets that we've generally found living under a decomposing wind crust that was the old snow/new snow interface. You can find this layer in and areas where the snowpack is deepest (North through East). Recent test slopes have all arrested after intial collapse on these layers. Slopes greater than 35 degrees are the most likely to overcome friction and produce an avalanche. 

    ENE aspect above treeline with a buried near surface facet layer. This slope collapsed when we stepped onto it before digging the pit.

Avalanche Discussion

As we continue to move farther away from our most recent loading event and our weak layers are adjusting to the stress, the obvious signs of instability such as audible collapses and shooting cracks will come less and less frequently. That doesn't mean the avalanche problem has fixed itself or gone anywhere. Persistent avalanche problems linger for weeks after a storm and their associated persistent weak layers take longer to heal than time is usually available to them. The best method at that point for gathering feedback on a suspect slope is to dig and get your eyes on the problem. An extended column test (ECT) and propogation saw test (PST) will provide some of the most valuable information during this period. If you find yourself performing either of these tests, please submit an observation! That information is invaluable when tracking these persistent weak layers.

Our last reported avalanche was on Monday Dec 14 on an East aspect up in Long Canyon. This was a persistent slab avalanche that failed on basal facets and was triggered from an adjacent low angle slope. In our more recent travels we have continued to reliably experience collapsing and shooting cracks on suspect terrain. Small test slopes, meant to guage the liklihood of producing an avalanche, all arrested after collapsing. Meaning they didn't avalanche. The lack of recent natural and skier triggered activity and results from tests slopes over the previous few days have all contributed to our current Moderate danger rating. Triggering one of these avalanches is still possible though and we should be evaluating terrain and snow carefully.

Terrain selection and managment is the single best tool we have right now in mitigating this avalanche problem. Sticking to slopes less than 35 degrees and considering how we actually manage skiing or riding a piece of terrain are extremely effective. Try and choose terrain that allows for safe regrouping on the descent and isn't exposed to terrain above you. Decide where this spot is going to be and make sure your whole party understands. Ski or ride one at a time to minimize exposure.  Always be mindful of what slopes may be above you. These are just a few thoughts that are always on my mind when I step out into the backcountry. Especially while trying to mitigate the uncertainty associated with a persistent slab avalanche problem. 

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