Boletín de aludes

East Slopes North

Northwest Avalanche Center
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Peligro de aludes

Thu
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

Warm temperatures should make wet avalanches on slopes in direct sun your primary concern on Wednesday. Don't linger beneath steep faces, rocks, or cliffs where these avalanches are more likely to initiate. If you're in the eastern mountains, consider that triggering large avalanches on older buried weak layers may still be possible at mid to upper elevations. 

Problemas de aludes

  • Loose Wet

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

    For southern aspects, Wednesday won't be the first day of sun on fresh snow. However, warm afternoon temperatures will likely break down recently formed thin surface crusts on these sunny slopes, and you will see natural wet loose avalanches run in steep terrain. Rocks and cliffs still holding snow are prime locations for these avalanches to begin, so monitor overhead terrain and don't linger under these features in the warm afternoon sun. You can also trigger these slow-moving avalanches that have a knack for grabbing your feet, skis, or machine and pulling you downhill. So consider sticking to lower angle and less consequential terrain if you travel on sunny slopes later in the day. Wet snow surfaces, rollerballs, and snow that feels sticky are the first signs that wet loose avalanches are becoming more likely. 

  • Wind Slabs

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

    If you seek out shadier aspects for recreation on Wednesday, you may still find lingering pockets of wind slabs. We expect most of these slabs to be small and are becoming more difficult to trigger. However, don't let your guard down in steep terrain near ridges, rocks, cliffs, and confined features where even small avalanches could have high consequences. Cornice features, textured surfaces, and stiff snow over softer snow are all ways to identify wind slabs. Before committing to steep slopes in wind exposed areas, look for signs of instability in small test slopes, such as long shooting cracks. If you identify any signs of unstable snow, steer around these stiff pillowlike slabs or choose lower-angled slopes or entrances off ridgelines to avoid triggering a wind slab avalanche. As usual, with rapid weather changes, there is always some added uncertainty. Although we don't expect widespread cornice failures, it will be something to consider. If you observe large, overhung cornices sitting in the sun, avoid lingering below them and consider giving them wide margins by traveling far below them in the terrain.

    (1/5/2023)

    Cracks shoot through wind-drifted slabs just below a ridge. 

    Photo: Frank Clements

Avalanche Discussion

On Monday and Sunday, observers triggered small avalanches in pockets of freshly drifted snow. These occurred on a mid-slope roll on the Lyall glacier and at 6,900ft, SE aspect near Snagtooth Ridge, respectively. On Monday, observer Willie Webster found large (5-10mm) rounding buried surface hoar (Jan 5) near the crown of one of many avalanches that ran during the MLK storm near Rainy Pass.

The January 5th buried surface hoar is the main persistent weak layer we've been tracking in the zone. Near Washington Pass, it's ~2' below the snow surface and is unreactive. There haven't been any human-triggered avalanches on this layer since 1/12. Willie's observation near Tiffany Mt on the 19th indicated that triggering avalanches on the 1/5 surface hoar may still be possible in this portion of the zone. Persistent slab avalanches are unlikely in the foothills and low-elevation mountains of the Methow Valley, where rain surrounding MLK weekend transformed weak layers to melt forms. On Wednesday, Willie investigated a very large slide in Liberty Bowl/Blue Lake Pk that likely occurred on January 13 or 14th. The avalanche failed on the Christmas crust and stepped down to the mid-November facets (11/22). The crown depth was 5-8 feet. While this avalanche was an anomaly, a look through the depths of our database shows other natural avalanche cycles on these layers.

The last significant cycle of avalanches occurred around the 13th and 14th, with wet avalanches in the lowland hills gouging to the ground and multiple very large natural avalanches running on persistent weak layers higher in the mountains. Check out the media reel below and our observation platform to see more.

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