Boletín de aludes

Snoqualmie Pass

Northwest Avalanche Center
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Peligro de aludes

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

Lo esencial

An ongoing storm, multiple known weak layers, and recent avalanches all point toward being a bit cautious on Wednesday. While wind drifted snow will be the most obvious hazard, slabs failing on older weak layers could be very hard to assess and manage. Stick to simpler, lower angled, or treed terrain. 

Problemas de aludes

  • Wind Slabs

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

    The first part of this storm won’t bring a ton of snow. So, while you might trigger a very shallow slab in sheltered terrain, the real hazard will be where the wind drifts the snow into deeper larger slabs. This will be most common in exposed areas and at higher elevations. As the day goes on, these potential avalanches will only become bigger and more widespread. 

    Fortunately, the obvious clue will be right in your face… blowing snow. Make note of where the local winds are drifting snow and loading slopes. While some of these slabs will be small and relatively easy to manage, they could trigger a larger persistent avalanche.

    (12/13/2024)

    Example: Blowing snow and firm pillow-like drifts are great clues to anticipate wind load slopes. 

    Photo: ONP Rangers

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1.5–2.5

    For weeks we’ve been talking about the January Drought Layer (JDL) and 1/10 facets (about 3ft below the surface) as being the main persistent slab culprits. They are still there, but you will also want to check out the 2/13 interface. This layer produced numerous natural avalanches on Tuesday. On more southerly slopes, this interface is often a melt-freeze crust with rimed grains above. On shadier aspects, it could be surface hoar or facety grains. No matter what, several older weak layers exist in the snowpack that could produce slides. 

    Don’t expect a lot of obvious signs of instability. The only way to really check these layers is to dig and look. Numerous snowpack tests over several weeks, across multiple locations all show the same thing, these layers are still there and can result in avalanches.

    These slabs would be most likely in more complex terrain with rocks, rollovers, and hanging slopes. While we’re most concerned about shaded aspects, with the inclusion of the 2/13 interface, some southerly slopes could also be in question.

    (2/18/2025)

    This very large natural avalanche released Tuesday afternoon. on the backside of Chair Peak. It's uncertain exactly which of the older snow layers failed in this slide. WSW, 5400ft, SS-N-D3-R2-O

    Photo: Zack Novak

Avalanche Discussion

Here we go again. Another storm, another round of new snow issues, and another interface. This new snow will accumulate on a new melt-freeze crust on sunny slopes, and likely well settled powder on shadier aspects. As the new snow accumulates over the 2/18 interface expect the danger to slowly rise. 

We’ve been gradually increasing the amount of snow over the persistent weak layers. Particularly, the JDL and 1/10. We might not have hit the tipping point but one larger natural D3 avalanche on Tuesday could be the proverbial 'canary in the coalmine.' Or that slide might just be a deeper pocket over the 2/13. Either way, the snow is stacking up and so are the weak layers. 

At lower elevations expect wet heavy snow. In some places, you may even be able to push a small wet loose slide. Even if it isn’t very big, it might not let go and could carry you into a creek or over a cliff.

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