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
2 · Moderado
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Desactualizado: este boletín caducó last year. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Record high temperatures and hot spring sunshine will increase the chance for large wet snow avalanches. These slides will be easy to trigger and may occur naturally. Start and end your day early and don't linger in gullies or beneath large, rocky slopes.

Problemas de aludes

  • Loose Wet

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

    Wet loose avalanches are likely on steep slopes. Yesterday, we witnessed these avalanches cascading out of warm rock bands and found them easy to trigger on steep slopes (video at right/below). Rollerballs and a slushy snow surface are clues that the snow is heating up, and wet avalanches may soon follow. 

    While many will be small, they can grow large enough to knock you off your feet or bury you in channeled terrain. Even small slides are consequential above terrain traps such as gullies, creeks, and thick timber. Plan for an early day, and avoid lingering under big avalanche paths and steep, rocky slopes. 

    Additional Discussion: Cornices are large and may be unstable. Some may release naturally as they sag during the heat of the day. They can break further back than expected—give them a wide berth when traveling along ridgelines.

  • Wet Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2–2.5

    Large wet slab avalanches are most likely at middle and upper elevations where meltwater reaches buried weak layers. Weak layers of facets and crust + facet combinations are most prominent above 8000' on slopes facing E-NE-N-NW. Today's record high temperatures and hot sunshine will continue to push meltwater deep into the snowpack, and the potential for large wet slab avalanches is on the rise. 

    This problem is hard to predict and not easily managed. Given the weak overnight freeze, surface crusts will break down quickly, and meltwater generation will begin again early this morning. Your best bet is to avoid travelling through and under avalanche paths with cliffs or rock outcroppings near the start zones.  

Avalanche Discussion

Our snowpack is undergoing rapid change. Today is forecast to be the hottest day of the year as temperatures climb into the mid-50s F at upper elevations. Couple this with strong spring sunshine and a weak overnight freeze, and conditions are primed for some large wet snow avalanches. 

Yesterday in the Boulders, we made this short video explaining a typical progression of wet snow avalanche problems. Sun on dry snow can create meltwater at the surface, causing rollerballs or pinwheels. Extended sun will wet a thicker layer of snow at the surface, and before long, these rollerballs are joined by small wet loose avalanches. Continued melting at the surface can push water deeper into the snowpack, allowing for larger, gouging wet loose avalanches or destructive wet slab avalanches. 

Overnight, mild near or above freezing temperatures and clear skies have allowed the snowpack to cool, but this only put a temporary band-aid on the problem. Below any thin surface crust is a wet, mushy snowpack. The sun's return will weaken crusts, and the process continues, pushing meltwater deeper. Over the past couple of days, we observed and received reports of numerous loose snow avalanches and some slab avalanches up to 2' thick. This process will continue today, with the potential for deeper, more destructive wet slab avalanches on the rise. 

With wet snow avalanche problems, the slope-to-slope variability is high, especially once meltwater begins to move through the snowpack. Subtle differences in terrain orientation, amounts of wind, and cloud cover can make a huge difference. Rather than trying to predict when a slope is reaching its tipping point, I'm more comfortable knowing that I simply don't know. This uncertainty leads me to safer, lower-angled, simple terrain that minimizes overhead exposure during the heat of the day. I'd recommend a similar approach. Give yourself wide safety margins and plan to start and end your day early.

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