Boletín de aludes

Banner Summit

Sawtooth Avalanche Center
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Peligro de aludes

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

Lo esencial

The avalanche danger will increase throughout the day as a storm impacts the area. Small natural avalanches will become more likely as snowfall intensity increases this afternoon and evening. Much larger human-triggered avalanches are likely on many slopes. These slides will be 2.5 to 3.5 feet thick, releasing on weak snow buried deep in the snowpack. Avalanches may be triggered remotely—from gentler terrain above, below, and to the sides of steep slopes.

The danger will increase to HIGH tonight. 

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    2–3

    Triggering a 2.5-3.5' thick persistent slab avalanche is likely on many slopes. Chris' video (above/right) exemplifies this problem. Persistent weak layers (sugary facets, surface hoar, or crusts) exist on most aspects and elevations. The weakest facets we've found are on shadier aspects.

    Thick slabs are more common as you climb into terrain that's exposed to the wind. Recently wind-loaded slopes with stiffer snow in the top couple of feet of the snowpack are the most likely to produce large avalanches. Snowpack cracking and collapsing are clear symptoms of an unstable snowpack. Tilt that collapse onto a steep slope, and you're flirting with an avalanche. Collapses can travel large distances releasing avalanches above you or on nearby steep slopes. 

    Unfortunately, avoidance is the only way to effectively manage this problem. Skiing or riding steep terrain is a risky roll of the dice. Today's storm will increase the odds of both natural and human-triggered persistent slabs. Sluffing, cornice breaks, or small storm slabs can act as effective triggers, "stepping down" to release a very large and dangerous slide.

  • Storm Slabs

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

    Two-day storm totals will reach over a foot by the end of the day today. Avalanches will become more likely as snow piles up this afternoon and into the evening. New snow is falling on a widespread weak layer of surface hoar occasionally paired with facets and crusts. Expect this interface to be touchy. 

    Many steep slopes will "sluff" naturally, especially during bouts of intense snowfall. In sheltered areas, small soft slabs may release (above/right). These slabs will grow in thickness throughout the day. In windier terrain at upper elevations, expect to encounter thicker, stiffer slabs. What doesn't release naturally, will likely be very easy to trigger and will be large enough to bury you.

    (12/9/2022) This small slab near Galena Summit failed after 4-6" of snow fell overnight. A dozen similar slides were observed along the roadway. These small slabs are indicators that the surface that we just buried is likely to be reactive with additional loading this weekend. As the snow piles up, similar slabs will grow in size and become increasingly hazardous.

Avalanche Discussion

It's snowing again this morning and we can expect another 1-1.5' of snow by the end of the day Sunday. This will bring 3-day snow totals in the Banner Summit Zone to 1.5-2'. Avalanche conditions were dangerous before this storm, and will get worse through Sunday. The avalanche danger will likely rise to HIGH tonight, and AVALANCHE WARNINGS may be issued. 

Today could go from dangerous to "get-out-of-the-way" by nightfall. Relatively safe routes this morning could turn dicey as you head back to the car. Expect the touchy surface under this storm snow to produce numerous small natural avalanches and plan your exit with this overhead hazard in mind. Small, manageable storm slabs this morning may be large enough to sweep you off your feet or bury you by day's end, particularly if you're traveling on slopes with wind-drifted snow.

Want more? Tune in to Ben's Weekend Update from the field for a quick recap of where we've come from and where we're headed this weekend. 

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