Boletín de aludes

Banner Summit

Sawtooth Avalanche Center
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Peligro de aludes

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

Lo esencial

Avoid steep slopes—and the areas beneath them—if you're traveling in a wet, sloppy snowpack. Natural and human-triggered wet avalanches are most likely on sun drenched, rocky slopes. Stability can quickly worsen as intense sunshine melts the snow. On slopes with cold, dry snow, triggering a large, thick avalanche is not out of the question.

Problemas de aludes

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2.5

    Natural and human-triggered wet loose avalanches are likely where, and when, the snowpack resembles oatmeal. Once the sun melts any surface crusts that formed overnight, you or your machine could fall into an unsupportable, soggy mess. 

    Many wet loose avalanches have gouged down near the ground on exposed upper elevation slopes with thin snowpacks (less than about 3 feet thick). The majority of the natural wet loose activity has occurred on rocky, W-S-E facing slopes in alpine terrain.

    Managing this problem is straightforward; stay off of and out from beneath steep slopes if you're sinking into a wet, mushy snowpack. Pay attention to the terrain above you, and minimize the time you spend on or beneath steep slopes receiving direct sunlight. Even small wet avalanches are surprisingly powerful, and wet loose slides make great triggers for the wet slab avalanches described below.

    Cornices: The warm weather is causing a lot of natural cornice fall. Cornice chunks are great triggers for wet loose or wet slab avalanches. Give cornices a wide berth. Beware of any avalanche paths that are guarded by large cornices and have wet snowpacks.

    (3/19/2024) Track of a large avalanche that was intentionally triggered by throwing a rock at a slope. This slide started on a SW aspect around 9,700' near Galena Summit. Similar avalanches are possible in this zone. 

    Photo: Ben VandenBos

  • Wet Slabs

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

    In recent days in other zones, Ben triggered large wet avalanches by throwing snowballs or rocks onto slopes and while on skis above avalanche starting zones. Also, we have observed several wet slab avalanches that released on their own (view Avalanches here). Natural and human-triggered wet slab avalanches remain possible today. Wet avalanches do not need human triggers to occur; they release on their own far more frequently than dry avalanches.  

    Accurately predicting real-time, slope-scale stability for wet slab problems is one step short of voodoo. Don't try to outsmart them.

    How do we manage this problem? Avoidance is the only reliable strategy. The prudent move is to stay off of and out from beneath large or consequential avalanche paths where you're sinking into a mushy snowpack. A thin surface crust will not eliminate the chances of triggering one of these beasts; slopes can remain unstable while water moves down through the snowpack. Cornice fall and smaller wet loose avalanches make great triggers for larger wet slab slides.

    (3/17/2024) This large wet slab avalanche was triggered on Sunday when Ben threw a snowball at the slope. It ran 1,400' to the valley below. 

    Photo: Ben VandenBos

  • Persistent Slabs

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

    Wet avalanche problems are the primary focus, but triggering a large, destructive avalanche where the snow surface has remained dry isn't completely off the table yet. These slides would fail on persistent weak layers (crusts, crusts and facets, or facets) in the middle or bottom of the snowpack. You're most likely to trigger one of these beasts in steep, rocky, wind-swept alpine terrain. Here, thin areas of the snowpack make it easier to trigger avalanches.

    Persistent Slab avalanches can release in surprising ways. You can trigger them from flat or low-angle terrain long distances away from steep slopes, and they can break far above you. They can break hundreds or thousands of feet wide. Before triggering an avalanche, you probably won't experience snowpack collapsing or other obvious signs of instability. 

     

    (3/14/2024) This large avalanche was triggered on ascent as three people booted up the final 20' to the saddle at the top. No one was caught. The avalanche broke 2-4+ feet deep on faceted snow. Sawtooth Mtns, N @ 9,900'.

Avalanche Discussion

Riders and skiers, including the SAC forecasters, are both more experienced and comfortable with dry snow avalanche hazard. Why is this?

  • Wet snow is complex and unpredictable. Stability can change rapidly as water moves down through the snowpack. 
  • For wet snow, our standard rules of thumb and tools (how much is it snowing/did it snow, how much snow is the wind moving, is the snowpack cracking or collapsing, what do snowpack tests show) are of no to little value. 
  • We have more practice with dry snow. We deal with dry snow for most of the season, and traveling in wet, unsupportable snowpacks is difficult and no fun—people tend to avoid it.

Evaluating wet snow hazard is a bit of a mind-warp; instead of a multi-day snowstorm, we are dealing with a multi-day solar storm . Due to the complexity of how water moves through and affects the snowpack, its very difficult to predict exactly when, and if, we'll see widespread wet snow avalanche cycles let alone accurately determine if a given slope is safe to ski or ride. 

Do we expect the mountains to put on a staggering avalanche show today? No. Would we be surprised if many destructive wet avalanches release naturally? No. 

Today is another great day to steer clear of consequential or complex avalanche terrain. The corn snow slope you safely rode or crossed beneath in the morning could be ready to release naturally hours or minutes later. The snowpack remains in an unpredictable spring transition period, and there will be plenty of time to ride or ski big, committing lines once the snowpack is freezing solidly at night. 

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