Bollettino valanghe

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Thu
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Avoid steep slopes with wind drifts or stiff snow on the surface to reduce the chances of triggering an avalanche. As you climb in elevation, you will encounter more potentially dangerous, wind-loaded slopes. Although not likely, some avalanches could fail on layers deep in the snowpack and be large enough to bury people or destroy vehicles. 

Conditions are more dangerous near the Smoky Mountains crest/Dollarhide Summit where more snow fell. Refer to the Galena Summit & Eastern Mtns Forecast if you're traveling in this area.

Problemi valanghivi

  • Wind Slabs

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

    Expect to find wind slabs, large drifts, and cornices in upper elevation and possibly exposed middle elevation terrain. The combination of snowfall and variable winds (different speeds and directions) added to existing slabs and is forming a new generation of wind slabs. Expect to find wind-affected snow in the usual locations—near ridgelines, beneath cornices, and on the sides of cross-loaded gullies—as well as near prominent terrain features lower on slopes and on aprons at the bottom of chutes.

    Some of the wind slabs may have formed above weak snow in the upper part of the snowpack and could be more sensitive to triggering than you would expect. Evaluating stability could be tricky in wind-affected terrain; check for crusts, weak faceted snow, and possibly buried surface hoar up to a foot below the drifts or slabs on any consequential slope you consider playing on today. 

    Cracks shooting out in front of you are a clear sign you could trigger wind slab avalanches. Pay attention to how the snow feels beneath your boards or sled. If you feel the snow stiffen or notice you're staying closer to the surface instead of sinking deep into the snowpack, you've found wind-affected snow and should avoid steep slopes. 

    The wind slabs are hazardous on their own and are also stressing the deeply buried weak snow creating the persistent slab problem in Problem #2. Smaller wind slab avalanches have the potential to "step down", triggering much larger avalanches. Professionals are avoiding traveling on slopes where the wind slab and persistent slab problems overlap.

    (12/31/2021) On Friday, NW winds were actively loading slopes - especially in the southern portion of the forecast area. This small wind slab in the Soldiers occurred naturally as a result. Photo: Soldier Mtn Ski Patrol

  • Persistent Slabs

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

    A mix of facets and crusts leftover from October snowfall make up the base of the snowpack on most shady middle and upper elevation slopes. Avalanches have failed on this layer following each major precipitation event this winter. 

    On Sunday, Sun Vally Heli Ski staff experienced a large, rumbling collapse just north of this Zone when the helicopter landed in a safe location. Public observers traveling in the Galena Summit area have also reported triggering large collapses in recent days. In steeper terrain, these collapses would be avalanches. The ongoing snowfall and wind are stressing the old October weak snow. While we don't anticipate widespread avalanche activity on this layer, it's nearly impossible to predict exactly which individual slopes are teetering on the edge of avalanching.

    How are local professionals managing this problem? They are generally taking it off the table by avoiding slopes where the old snow exists. This travel strategy is pretty easy to swallow given the excellent riding and skiing conditions on slopes lacking the old October faceted snow.  

     

    (1/2/2022) This large persistent slab avalanche was observed above Corral Creek, near Johnstone Peak. It failed on a N/NW facing slope at 8,600'. The terrain and trees below the crown limited its size, but the crown is over 500' wide.

Avalanche Discussion

EVALUATING 'MIDDLE-AGED' FACETED WEAK LAYERS

The layer of faceted snow near the ground on many upper and middle elevation shady aspects (NW-N-NE-E) and some upper elevation sunnier aspects is not the young, eager whippersnapper it was during the first big storm in mid-December. How is it showing signs of age?

  • Less natural avalanche activity with each successive storm
  • No recent remote triggered avalanches
  • Reports of large snowpack collapses becoming less frequent
  • Inconclusive snowpack test scores
  • Getting physically "shorter" - mechanical compression is making the layer thinner where the slab above it is more than a few feet thick

As weak layers—and people—age, they tend to mellow. The faceted, old October snow appears to be "mellowing". What should we expect as this layer transitions to its golden years? 

  • Unpredictable: The steady load from snow and wind could cause it to have a "mid-life crisis" on some slopes, while on other slopes it will gracefully age and fade into the sunset. 
  • Less communicative: It is difficult to tell how the October layer is feeling. Snowpack collapsing and unstable snowpack test scores will become even less frequent; but, a lack of signs of instability IS NOT a green light signaling the layer has been laid to rest.
  • Bursts of anger: It will be hard to tell its coming, but I'd expect to see some isolated angry outbursts—very large avalanches—before this weak layer is done.

What's the moral of the story? Triggering a large, destructive avalanche is still on the table as snow piles up today and later this week. Unfortunately, it's a lot easier to predict how this type of layer will behave when it is younger (during the first couple of big storms). There's a good chance we'll be able to write the obituary for the October snow in the coming weeks, but we're not writing it today.  

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