Bollettino valanghe

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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In sintesi

Numerous natural and triggered wind slab avalanches occurred yesterday. Watch for wind drifts in upper elevation and alpine terrain—these will remain touchy today. On very steep slopes facing the sun, wet snow avalanches will become likely as the day heats up.

Problemi valanghivi

  • Wind Slabs

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

    Thursday's spring storm produced a combination of new snow and wind, and numerous natural and triggered wind slabs were reported across the forecast area yesterday. Most of these were fairly small, but at least one (Gladiator Peak) was large enough to bury a person. Even small wind slabs can be dangerous in the wrong terrain, and yesterday many folks chose to bail on consequential objectives. See the Forecast Discussion and Media Gallery below for more detail on the observed activity.

    Many of these wind slabs formed on weak surfaces, including slick crusts, facets, or some combination of these. Wind slabs will likely remain touchy today, especially with a slight uptick in wind overnight. The good news is that they will be fairly easy to identify—avoid steep slopes where the snow feels denser, punchy, or hollow, or where you see the tell-tale surface texture from the wind. The bad news is that these wind slabs seem to be common enough in alpine terrain that navigating around them may be similar to walking through a minefield.

    (3/26/2021) Touchy wind slab at the head of Owl Creek. T. O'Connor photo.

  • Loose Wet

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    • Limite del bosco
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    Probabilità
    Likely
    Dimensione
    1

    A handful of small wet loose avalanches were reported yesterday, but a few clouds and relatively cool temps kept things from coming totally unglued. That may change today as sunshine and warming temps heat up the newer snow and make it more likely to slide off underlying crusts. If you find the surface snow becoming moist and sticky, you'll want to avoid slopes approaching 40 degrees. Expect natural wet sluffs to occur on steep, sun-drenched slopes during the heat of the day. Wet snow avalanches should be relatively small, but expect them to be larger and more dangerous in areas that received more snowfall from the last storm—such as the upper elevation reaches of the Pioneers, Boulders, and White Clouds.

    ADDITIONAL DISCUSSION:Dry loose avalanches are a concern on very steep, shady, and wind-sheltered slopes. This minor hazard can be amplified on consistently steep, larger slopes or confined terrain like chutes, where sluffs are harder to escape.

    (3/26/2021) Natural wet sluffs in the Sawtooths that occurred Friday afternoon.

Avalanche Discussion

MORE ON WIND SLABS...Yesterday produced a flurry of reports of sensitive wind slabs. This was due to a combination of a reactive wind slab problem and numerous folks out in the terrain where the problem existed. Most of the natural and triggered wind slabs were not large enough to bury a person (around D1 in size), but the wind slab problem was real enough that many parties bailed on their initial objectives and turned to Plan B. "Touchier than expected" was a common phrase in many of yesterday's observations. This illustrates three things about wind slabs: 1) Wind speeds reported at remote weather stations don't always tell the whole story. Mountain winds are a complex phenomenon that can't always be quantified by speed and direction. Sometimes the wind blows just along ridgelines, and other times it gets down into lower terrain and wreaks havoc all over the place. 2) The sensitivity of wind slabs can be tough to predict, and can often change from location to location. 3) As a result of 1) and 2), wind slabs can be unpredictable animals. That's why the best way to manage them isn't through evaluation, it's through avoidance. When you find wind slabs are too difficult to identify and avoid, it's time to step back—as many groups did yesterday.

Here's a summary of yesterday's activity (see Media Gallery or click on the links for photos):

  • A large (big enough to bury a person) natural wind slab avalanche occurred on Gladiator Peak, breaking about 200' wide. Numerous smaller slides released naturally in the Pioneers, Boulders, and Sawtooths.
  • Parties in the Boulders, Smokys, and Sawtooths turned back from their objectives due to wind slabs.
  • Skiers triggered several small wind slabs (intentionally and perhaps unintentionally) in the Pioneer, Boulder, Smoky, and Sawtooths Mountains.
  • In the Sawtooths, Ben remotely-triggered two avalanches from over 100' away.
  • Scott and I were in Hyndman Basin in the Pios where we found the 12+" of new snow had formed sensitive drifts in exposed terrain. We saw a natural wind slab avalanche and released a small wind slab on a steep test slope (photo, video).
  • Widespread wind ripples and dunes were apparent in alpine terrain across the forecast area (examples: Smokys, Pioneers).

Wind slabs will likely remain touchy again today, and a slight increase in wind overnight may have produced additional wind loading. If you head for steeper alpine terrain today, be sure to keep your eyes peeled and be mentally prepared to turn around. 

Be sure to catch up on what happened this past week in Scott's Weekend Update!

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