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
1 · Debole
Sotto il limite
1 · Debole
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In sintesi

Light snowfall and moderate winds may form fresh wind drifts at upper elevations—these will likely be small, but could be easily triggered. Avalanche releasing on weak layers buried 2-4 feet deep remains a possibility on very steep, rocky, wind-affected slopes at upper elevations. This problem will be most prevalent in the alpine terrain of the Boulder, White Cloud, and Pioneer Mountains. 

Problemi valanghivi

  • Persistent Slabs

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

    Early-season persistent weak layers are widespread throughout the Galena Summit & Eastern Mtns zone. In the deeper portions of this zone near Galena Summit south to Baker Creek, these layers are typically found in the bottom half of the snowpack and have been showing better stability. In the White Clouds, the weak snow near the ground is especially pronounced and produced a very large avalanche earlier in the month (see photo). In the windswept, alpine terrain of the Boulders and Pioneers, the pattern of weak snow is especially variable. You're likely to find weak layers near the ground as well as sandwiched between old wind slabs. 

    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.

    ADDITIONAL DISCUSSIONToday's storm is forecast to produce 2-4 inches of new snow in this zone, and this shouldn't have a huge impact on the avalanche danger. In fact, the age-old phrase "lipstick on a pig" comes to mind. But with moderate winds expected, look for thin, fresh wind slabs in upper elevation terrain. These will be forming on a variety of slippery surfaces including icy crusts and facets. So, while small, these could be sensitive to the weight of a skier or rider. 

Avalanche Discussion

Today's storm should produce less than about 4 inches of new snow in the mountains south of Galena Summit. This snowfall shouldn't have a huge effect on today's avalanche danger, but fresh, thin wind slabs may form in upper elevation terrain. Due to the old, slick surfaces they're forming on, they could be touchy but are likely to be small in size. On the other end of the likelihood/size spectrum, the persistent slab problem continues to nag us. While unlikely, triggering one of these would produce an avalanche plenty big enough to bury or kill you. 

In the Sawtooth & Western Smokys and Banner Summit zones, our attention is slowly shifting from deeply buried persistent weak layers to storm-related surface instabilities. Even though today's storm isn't looking as promising as it was a few days ago, up to 8 inches of new snow could accumulate in these mountains by the end of the day. With the low-confidence weather forecast, this storm could produce even more (or of course, less). Moderate westerly winds today will easily transport this new snow into fresh, soft wind drifts on upper elevation ridgelines and other prominent terrain features. These wind slabs will form on old snow surfaces that include anything and everything—wind-hardened surfaces, stiff drifts, sun crusts, and near-surface facets. All of these tend to be slippery, and today's fresh wind slabs will likely be touchy on steep slopes. If the storm produces more than forecast—say, greater than about 8 inches—we may begin to see a storm slab problem on very slopes that are sheltered from the wind.

It's easy to get cavalier about these surface instabilities after dealing with persistent slabs problems all winter. When faced with these "manageable" problems, you may find yourself in consequential terrain where even a small slide can be every bit as dangerous as a big, bad persistent slab. Remember that the avalanche danger is only one part of the equation, the other components are your level of exposure to the avalanche hazard and the consequences of triggering a slide. Often our overconfidence at managing surface instabilities leads us into terrain where the exposure and consequences can be dangerously high.

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