Boletín de aludes

East Slopes Central

Northwest Avalanche Center
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Peligro de aludes

Wed
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
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

Dangerous avalanche conditions on Tuesday will require that you keep a large margin of terrain between you and slopes steeper than 35 degrees. You can trigger surprising avalanches that may break widely over terrain features, especially where the wind forms drifts of new snow. Warning signs of the avalanche danger include whumphing collapses, drifts of freshly blown snow, and a layer of weak, sugar-like snow over a crust about 8-12" below the surface.

Problemas de aludes

  • Wind Slabs

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

    Avoid mid to upper elevation slopes steeper than 35 degrees where you find the wind forming fresh drifts and deeper areas of snow on the leeward side of ridges. Tuesday is a day to avoid wind loaded terrain. If triggered, any slope could break into older weak layers resulting in a very dangerous Persistent Slab avalanche (see below).  The most dangerous slopes will be near and above treeline where the wind drifts thicker slabs on an already weak snowpack. Pay attention to which slopes receive wind loading and the direction of the wind. Watch for blowing snow as an indicator.

    Moderate to strong winds will increase and shift from south to west through the day. Expect avalanches to be larger at higher slopes and to grow bigger as the day goes on. Slabs will also be bigger on the west side of the zone at the heads of the Salmon la Sac, Teanaway, Icicle, Nason, and Entiat drainages. These avalanches will be smaller in the Wenatchee mountains near Blewett Pass and Mission Ridge. 

    (12/12/2020) Blowing snow captured in the foreground on the summit of Rock Mountain. Looking south towards the south peak. Will Govus photo

  • Persistent Slabs

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

    Persistent slab avalanches are very dangerous and can catch even the most experienced backcountry travelers by surprise. Put extra space between where you travel and any slopes 35 degrees and steeper. Stay far away from convex rollovers and steeper slopes. Do not stop or linger at the bottom of avalanche paths. Make sure to stop well out from under and off to the side of any terrain steep enough to avalanche. Use clues like broken trees, trees stripped of uphill branches, and a lack of vegetation to avoid the runout of avalanche paths. Until we know more about the nature of these avalanches, consider all slopes 35 degrees and steeper guilty until proven inocent. 

    Observers have reported a layer of weak facets (1.0-1.5mm) resting on a crust that formed in the past week. Near the Cascade Crest, you can find this week layer about 8-16 inches (20-40cm) below the surface. On Monday, observers in the Highway 2 corridor near Lost Lake, as well as close to Stevens Pass, reported collapses up to 100ft in diameter and snowpack tests that indicate propagation.

    (12/14/2020) Observers found up to 8 inches of snow over a facet crust combo near Lost Lake. They reported whumphs as big as 100ft across on this weak layer.

Avalanche Discussion

By the end of Tuesday, you can expect 4-7" of snow near the Cascade Crest and 2-3" in the Wenatchee Mountains. This will be accompanied by moderate to strong wind and warming temperatures. Below 4,000ft you may find moist snow surfaces and you may be able to trigger wet loose avalanches. The avalanche danger will be the greatest on the west side of the zone. In the Wenatchee Mountains near Blewett Pass and the eastern foothills of the Cascades, you may find less dangerous conditions along with less snow.  Expect shallow snow cover at low elevations and bare ground particularly on low south-facing slopes. Typical early season hazards can be expected with open creeks, stumps and rocks. 

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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