Boletín de aludes

East Slopes Central

Northwest Avalanche Center
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Peligro de aludes

Sun
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

As the day progresses and new snow starts accumulating, the likelihood of you triggering an avalanche in fresh wind-drifted snow or worse, a deeper buried weak layer will increase.  Be mindful of changing conditions and give yourself some space from steep, upper-elevation wind-drifted areas.  Default to lower angle slopes and ridges to reduce your exposure.  

Problemas de aludes

  • Wind Slabs

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

    As winds and precipitation ramp up, newly forming wind slabs will start to develop. These will likely be shallow in nature, however they may become reactive during the later hours of the day, especially if they sit on a recent layer surface hoar or near-surface facets. You can find these wind slabs on the down-wind side of ridges, below cornices, and peppered in the alpine.  As winds ramp up and new snow piles up, give yourself some space from steep, convex slopes - specifically on the lee-side of ridges and in the alpine. 

     If you find yourself traveling at higher elevations on shaded slopes ( N-NE- E), consider the consequence of a wind slab stepping down into a deeper buried weak layer and producing a much larger, destructive avalanche. 

    (12/3/2022)

    Actively blowing snow, freshly building sharp cornices, and textured surfaces. All easy-to-identify signs of wind-loading. Use visual clues like this to help you identify slopes of concern on Saturday. 

    Photo: Dallas Glass

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2–2.5

    On Thursday, the third skier on a slope triggered a large and surprising slab 1-2ft deep on a NE aspect at 6,200ft in the eastern part of the Stevens Pass zone. It ran on large surface hoar on firm bed surface, triggered from the shallower area. So, contrary to popular belief, we still have a persistent slab problem. The slide even broke through the MLK crust which was about 5mm thick in this location. 

    You will most likely find this lingering weak layer at higher elevations on N-NE- E aspects above 6000 ft. These are the most likely spots where the MLK crust is thin or even non-existent. The distribution has proven to be spotty and not everywhere. So identify this layer by digging 2 ft down and looking for a thin gray line of buried surface hoar.  

    With the uncertainty regarding the distribution of this weak layer, it will be best to give steep open slopes a wide buffer at these elevations. You can reduce your exposure by traveling on ridges or slopes less than 30 degrees. 

    (1/19/2023)

    Large avalanche on a layer of buried surface hoar. NE at 6,200ft on Jim Hill. The crown was 1-2ft deep.

    Photo: Ryan Minton

Avalanche Discussion

Saturday will be defined by increasing hazard as the day progresses, especially knowing we have a tricky snowpack and uncertainty regarding the reactivity of older buried weak layers.  At the start of your tour you may only notice a few flurries. However, as the day progresses new snow will start to accumulate, winds will ramp up, and the red flags might be in your face. It will be important to be on top of your game and be in tune with the changing weather conditions.

On Friday, Josh and I traveled into the Blewett Pass area. We were treated  with sunny, calm weather and decent riding conditions. The calm and clear nights have caused snow surfaces to become weak and sugary.  In most locations we traveled we observed surface hoar and near-surface facets sitting above the MLK rain crust.  Keep this on your mind as you travel, since it could be tomorrow's buried weak layer. 

If you get out into the mountains, let us know what you see by submitting a public observation!

 

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