Bollettino valanghe

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

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. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    Multiple weak layers exist in the upper few feet of the snowpack:

    1. Surface hoar is buried 1.5-2 feet deep on many sheltered, shady (W-N-E) slopes. This layer produced a number of triggered slides during the second half of January. While it's showing signs of improvement, surface hoar can be a notoriously unpredictable weak layer.
    2. Recent storms have favored this zone and are starting to bury newer weak layers consisting of facets and/or crusts that formed during recent dry spells. Observations from the Sawtooths this past week are indicating some early signs of instability on these layers.

    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. 

    A skier triggered this 1-2 foot thick avalanche on Sunday Jan 29th on a N-NE aspect at 9100' near Titus Ridge. It failed on a layer of buried surface hoar.

  • Wind Slabs

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

    Sunday's storm brought 4-10" 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.

    (2/6/2023) This small wind slab was observed in the Sawtooths. It failed on an ESE-facing slope at 9,100' near McDonald Peak.

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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