Boletín de aludes

Snoqualmie Pass

Northwest 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 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

A stormy day at Snoqualmie Pass should result in wind slab development near rocky chutes or convex slopes. Slabs may exist lower in the terrain or on different aspects than you're used to finding them.  Warming temperatures throughout the day may result in mixed precipitation, complicating the avalanche picture.

Problemas de aludes

  • Wind Slabs

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

    Winds are forecast to crank through The Pass on Friday, resulting in a new crop of wind slabs on leeward slopes. Since the wind direction will predominantly be from the east, these slabs may form on different aspects than you typically see them. East wind events often result in more cross-loading or mid-slope loading than normal. Add it all up and these slabs could exist in unusual locations, so don't get caught off guard. Luckily, the clues and tricks are largely the same. Look for actively blowing snow, new cornices, or fresh drifts behind objects to help identify wind-loaded aspects. You can then avoid specific terrain features where wind slabs like to form, such as leeward ridgelines, confined gullies, the base of rocks, or convexities. 

    (1/2/2025)

    A human-triggered slab on a convex feature in the Alpental Valley on 1/2. This one is shallow, but they may be bigger on Friday after another day of snow and wind-loading.

    Photo: Nick Constantine & David Dunphy

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    This storm has a warming trend associated with it. We already talked about the strong winds, which will pull cold air through the Pass. These competing weather factors will likely result in a variety of precipitation types such as snow, freezing rain, and eventually rain at lower elevations. With the threat of rain, comes the possibility of wet avalanches. This problem may not occur if the snowpack is first capped by freezing rain or if there is no dry snow for rain to fall on. But in areas further away from the draw of the east flow, it could be more likely. If it's raining on dry snow and you see rollerballs or new avalanches occurring, head for lower-angled terrain keeping aware of what's above you. 

    (12/28/2024)

    Small wet loose activity on a road cut from a warm and wet day last week.

    Photo: Dallas Glass

Avalanche Discussion

On Thursday, NWAC forecasters and avalanche professionals in the Alpental Valley observed a well-settled upper snowpack, a few inches of new snow, and variable winds. Backcountry travelers further up the valley reported triggering a shallow wind slab on a convex feature. Prior days brought reports of multiple human-triggered avalanches up to size D2 in wind-loaded terrain throughout the zone. Most of these occurred in snow from last week's storm parade. 

After a short break, we're back to stormy weather on Friday and there will be a resulting increase in the potential for human-triggered slides. Although older layers could fail during this storm, the more likely scenario is that you'll be dealing with avalanches confined to the new snow and wind.

The wildcard will be freezing levels and the resulting precipitation type within the zone. Several different scenarios could play out involving snow, rain, and freezing rain. Apart from the wet avalanche potential mentioned above, warming temps could create an upside-down snowpack, leading toward a shallow storm slab problem. These likely shouldn't be deep enough to warrant a problem on their own, but keep an eye out all the same. 

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