Boletín de aludes

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Peligro de aludes

Wed
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

You're more likely to trigger avalanches on wind-affected slopes with recently formed drifts or slabs. On slopes that are sheltered from the wind, triggering a 1-2 foot thick avalanche is not out of the question. Consider the consequences of a slide before committing to avalanche terrain. Even small slides can be dangerous if they wash you into a gully, trees, or over cliffs. 

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1.5–2.5

    Multiple weak layers exist in the upper few feet of the snowpack. The most prominent of these is buried surface hoar down 1-1.5 feet on many sheltered, shady (W-N-E) slopes. This layer produced a number of triggered slides during the second half of January. Newer weak layers consisting of facets and/or crusts formed during recent dry spells and are just now starting to get buried.

    While it's been over a week since the last reported persistent slab avalanche (photo above/right), triggering one remains possible on some slopes—primarily those over about 35 degrees in steepness. These layers could produce an avalanche large enough to bury you, but even small slides can be dangerous if they wash you into a gully, trees, or over cliffs. 

    In addition to the layers in the upper snowpack, older weak layers (crusts and/or facets, occasionally surface hoar) exist deeper in the snowpack. These are buried beneath dense, 2-4+ foot thick slabs. While triggering them is unlikely, it can't be ruled out in rocky, wind-affected, alpine terrain. The upper elevation, wind-affected terrain of the Pioneers, Boulders, and White Clouds comes to mind.

    (1/30/2023) This 1-2 foot thick, skier-triggered avalanche failed on a layer of buried surface hoar. Surface hoar is frequently found in shady, partially treed locations like this. N-NE aspect near 9100' in the Salmon River drainage near Galena Summit.

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    Sunday's storm brought a bit of new snow and a healthy dose of wind. Ridgetop winds eased yesterday but may have remained strong enough to continue to load some slopes. Be on the lookout for fresh wind slabs near ridgelines and on the sides of mid-slope features like gullies and ribs. Though likely to be small, these wind slabs could be sensitive to your weight and are adding weight to the buried weak layers described above.

    As you travel through the mountains, look for signs that the wind has been at work. Dunes, pillows, and ripples on the snow surface indicate that the wind has been transporting snow. Cracks shooting out from your skis or machine are a clear sign of an unstable slab.

    (1/29/2023) This recent small wind slab released naturally on Titus Ridge near Galena Summit. It failed on a E/NE-facing slope at 9,600'.

Avalanche Discussion

While there are still some concerns about deeper weak layers—especially in the windswept, alpine reaches of the Pioneers, Boulders, and White Clouds—over the past month, most of the action has been happening in the upper few feet of the snowpack.

If you've been following the forecast, you've read about a layer of surface hoar that was buried in early January. This layer was most reactive in the Sawtooths & W Smokys and Banner Summit zones where it was buried beneath more snowfall, but triggered slides occurred in the Soldiers and near Galena Summit. The most recent avalanche on the buried surface hoar occurred near Titus Ridge on January 29th (report). In most locations, this layer is showing signs of improvement. However, surface hoar is an unpredictable weak layer and most of us aren't ready to write it off just yet.

Dry weather during the second half of January produced newer weak layers, ones that we're more familiar with: near-surface facets, often near crusts. Since January 27th, two smallish storms (both combined with wind) have begun to slowly load these newer weak layers—especially in our northern zones that received more snowfall. Early signs of instability such as cracking and poor snowpack test scores were observed last week in the Sawtooths, but there hasn't been quite enough snowfall yet to create a widespread problem. Another small storm is forecast for tonight—again favoring our northern mountains—which will continue to incrementally load these new weak layers. 

While the danger is MODERATE and conditions aren't especially dangerous, there is enough complexity in the upper snowpack—primarily in the mountains north and west of the Wood River Valley—that it's worth using additional caution. Slopes over 35 degrees, especially those with recent wind loading, deserve respect. Spend a bit of time thinking about the consequences of triggering and being caught in an avalanche in the terrain you are in. Even small slides can have bad outcomes on slopes with cliffs, trees, and terrain traps. 

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