Bollettino valanghe

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Avoid slopes where the wind recently formed drifts or slabs to reduce the chance of triggering avalanches.  Pay attention to the consequences of being caught in even small slides in terrain with rocks, cliffs, trees, and terrain traps.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1.5–2

    What is it? Although it's not likely, the most plausible way to get in trouble is in wind-affected alpine terrain, which Ethan explains in the video to the right/above. There is an outside chance of triggering buried surface hoar down 1-1.5 feet, but the evidence is growing harder to find. See the Forecast Discussion below for more information on the Wood River Valley conditions. 

    Where is it? You're most likely to find the problem where the wind has loaded slopes or stiffened the snow surface. The surface hoar is most problematic in somewhat protected, middle-elevation terrain that faces NW-N-NE. These layers are most likely triggered on slopes steeper than about 35 degrees. 

    How can you recognize it? Wind-loaded slopes have harder surfaces and a distinct appearance (video to right/above). You may or may not experience snowpack collapsing and/or cracking while traveling. These red flags are obvious signs of instability. The surface hoar layer is subtle and may not "jump out at you" when searching for it in a snowpit (see photo here).          

    How can you manage it? You can reduce your risk by avoiding very steep (greater than about 35 degrees), shady slopes (facing W-N-E) with hard or stiff wind-blown snow at the surface—especially those with ugly consequences if you are caught in an avalanche. Persistent slab avalanches may break wider than expected or higher on the slope above you. 

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    What is it? Recent wind-affected snow is sitting on top of fragile, sugary facets. The natural avalanche (picture to right/above) released on Wednesday during an NW wind event. Small avalanches can be more dangerous when they sweep you over cliffs like in this photo or into trees and other terrain traps. 

    Where is it?  You may find wind slabs near ridgelines, on the sides of gullies and chutes, and near prominent mid-slope terrain features. 

    How can you recognize it? Cracks shooting out from your skis or sled are an obvious sign of instability. Watch for drifts, dunes, and ripples on the snow surface. Wind slabs can have a smooth, chalky appearance and feel and sound hollow, like a drum. Wind-deposited snow will be stiffer and keep your skis or snowmobile on or closer to the surface.       

    How can you manage it?  The easy move is to avoid obviously wind-loaded slopes steeper than about 35 degrees. Hard slab avalanches can behave unpredictably, breaking above skiers and riders. Notice how far back on the ridge the slab pulled away in the above-mentioned natural avalanche. Small triggered wind slabs can potentially entrain snow or "step-down" to buried persistent weak layers (Problem 1) lower on slopes, causing a larger destructive avalanche.  

    (2/8/23) This wind slab released on an east-facing slope near 6200' above the Big Wood River in Hailey. This avalanche likely occurred in the early morning of Feb. 8 with increased NW winds.

Avalanche Discussion

WOOD RIVER VALLEY WEAK SNOW

The best chance of triggering an avalanche is on slopes steeper than about 35 degrees where you can kick off a small loose avalanche or wind slab that entrains more snow as it picks up speed.  Since this area hasn't received much snow in the last month, most of the upper snowpack has turned into weak, sugary facets. Playing in steep terrain can produce "facet-lanches" in this snowpack. These avalanches start at a point and entrain more weak snow as they descend the slope (see field report). They aren't usually big enough to bury you. However, they become dangerous when riders get knocked over and carried through trees, cliffs, gulleys, or other terrain traps.

On Wednesday, a party of skiers near Carbonate Mountain triggered a loose avalanche (observation, photo). One of the skiers initiated the weak surface snow that picked up speed, gathered more snow, and knocked them down. Luckily, they regained control, "but if it had dragged the member of our party through the pinch, it would not have been pretty." Loose avalanches can pick up speed quickly and have enough debris to knock you over. Avoiding slopes steeper than about 35 degrees which end in a terrain trap will increase your chances of surviving these small avalanches.

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