Bollettino valanghe

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

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Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 7 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Wind events over the past week have blown the recent snowfall into slabs and drifts in upper elevation and alpine terrain. Avoid steep slopes where you find wind-drifted or pillowed snow. Slopes where you could trigger weak layers buried 2-4 feet deep are becoming few and far between, but it may remain possible on very steep, rocky, wind-affected slopes at upper elevations. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    Early-season persistent weak layers in the lower snowpack are widespread throughout the Galena Summit & Eastern Mtns zone. What's less consistent is the nature and stability of these layers. 

    The thin, windswept snowpack of the Boulder Mountains did not respond well to this past week's wind events, and several large, natural persistent slab avalanches occurred as a result (see observation and photos below). In the White Clouds, a very large slab avalanche released a week ago on faceted snow at the base of the snowpack (photo to right). It broke over 500 feet wide, 4-6 feet deep, and covered snowmobile tracks from the previous day. Meanwhile, these same weak layers in the Galena Summit and Baker Creek area are showing better stability.

    While triggering a persistent slab avalanche is generally unlikely, it remains possible in terrain with the following characteristics:

    • Steep: slopes in prime-time avalanche terrain around 35-45 degrees.
    • Wind-affected: heavily wind-loaded by past or recent wind events.
    • Alpine flavor: complex, windswept terrain with rock ribs, cliff bands, or convexities.

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    The wind events of the past week have finally ceased, but we'll continue to deal with the aftermath for a few more days. These strong winds produced a number of small to medium-sized natural and triggered wind slab avalanches across the forecast area.

    Fortunately, these wind slabs will be easy to identify. Watch for snow that is denser than snow found on wind-sheltered slopes and tell-tale clues such as surface texture and a pillowed, drifted appearance. These will be less sensitive today, but I'd still avoid steep slopes where you find these indications of recent wind loading.

Avalanche Discussion

As we enter the first period of stable weather in quite some time, it's a good time to do a "State of the Union" on our current snowpack. 

The Soldier & Wood River Valley snowpack is the shallowest and weakest, especially in the mountains above Ketchum and Hailey. As is not uncommon in this area, there is plenty of weak, faceted snow—what's lacking is a slab of cohesive snow atop it. Unstable slopes are largely limited to where recent and/or past wind events have created dense or stiff snow in the upper pack. This was the case with a slide triggered during control work last week on Baldy. Storms earlier this winter favored the western half of this zone, and the snowpack there is more similar to Galena Summit.

The deepest snowpack exists in the Sawtooth & Western Smokys and Banner Summit zones. While these areas had thin snow at the start of the winter, they were heavily favored by the extended storm cycle at the start of the New Year. The early season weak layers are buried 4-6 feet deep, meaning that triggering an avalanche is difficult but likely unsurvivable. Avoiding thinner "trigger points" is the name of the game—these are more likely to be found in very steep, rocky, alpine terrain that is prevalent in the Sawtooths but less so in the Banner Summit area.

Finally, the Galena Summit & Eastern Mtns zone is the monkey in the middle. There is a great deal of variability across this zone, but it all falls somewhere between the two scenarios described above. The thin, windswept snowpack of the Boulder and Pioneer Mountains has characteristics of the Wood River Valley, where wind slabs sitting atop weak, faceted snow are the main concern. The Smoky Mtns of Galena Summit and the Baker Creek area have a bit deeper snowpack, with early-season weak layers buried 2-4 feet deep. In the White Clouds, the faceted snow near the ground seems especially pronounced—just a week ago, a monster broke over 500 feet wide and 4-6 feet thick.

So there you have it—the current State of the Snowpack. Just don't rip it in half...

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