Bollettino valanghe

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

Avalanche conditions are dangerous. You are more likely to trigger avalanches involving dense, 2-5 foot thick slabs in upper elevation terrain, but large avalanches are possible in sheltered terrain as well. Avalanches can be triggered from long distances from where the slide releases and can break much wider than expected. Conservative terrain selection is encouraged.

Problemi valanghivi

  • Persistent Slabs

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

    What is it? Multiple parties triggered avalanches in the past two days in the Galena Summit & Eastern Mtns. Dense 2-5 foot thick slabs are sitting over weak, sugary facets and/or crusts that remain sensitive to your weight. This structure caused over 300 recorded avalanches large enough to bury a person (map, list). The snowpack is slowly adjusting to last week's massive thump of snow and wind, and more new snow continues to delay the healing process of weak layers. 

    Where is it? The sensitivity and size of the avalanche vary from slope to slope (see the Forecast Discussion). The problem increases the higher up you travel from the trailhead. While springtime conditions may exist near the valley floor, a winter snowpack still clings below the recent snowfall. Last week, widespread avalanche activity was observed on all aspects and elevations.

    How can you recognize it? The countless number of avalanches can direct your attention to slopes capable of causing similar slides. These avalanches serve as a reminder of the terrain and the consequences of causing a destructive avalanche. Collapsing, cracking, and poor results from stability tests go down in frequency as the weak layer gets buried deeper in the snowpack. Triggering a large avalanche might be the first sign of instability you receive. 

    How can you manage it? Avalanches can be triggered from well above you on the slope you are riding or skiing. Tracks on a slope are not an indicator of stability. The slope might withstand the first, second, or even last person on it before producing a devastating slide. 

    ADDITIONAL DISCUSSION: In exposed middle and upper elevations, you can trigger fresh thin wind slabs.  Although these slabs will likely be small, they can be enough to knock you over and serve as effective triggers for releasing larger slab avalanches further down the slope. Steer clear of wind-affected terrain to minimize waking up the deeper problems lurking below. You are more likely to find these avalanches in the Soldier Mtns, where there is more new snow and windier conditions. Many large cornices are standing over steep terrain. Reduce your time being exposed to them from below and give them a wide berth while moving up ridgelines, as they tend to break away a lot further back than one can expect.  On Saturday, a group on Galena Peak cut a large portion of a cornice off and triggered a large avalanche (observation). 

    (3/16/2023) These large avalanches released on NW and NE aspects at 6,700' in Deer Ck.

Avalanche Discussion

When looking at a calendar, spring might be right on the doorstep, but today's snowfall is a reminder that winter is holding on tight. The new snow is unlikely to cause the same extraordinary avalanche cycle witnessed last week. It is slowing the healing process of the weak snow that formed during the January and early February drought. We find ourselves in a stalemate position, where a continued load isn't changing the sensitivity of triggering avalanches. 

Typically as we move away from large loading events, the likelihood of triggering slides decreases. That is not the case with more snow in the forecast. The western side of this zone (Soldier Mtns) is expected to receive the bulk of today's snowfall. Stay conservative with your terrain choices for the day. Here is a rundown of what to expect in the mountains:

  • Shady slopes facing NW-N-NE-E have a stack of faceted snow that developed during the extended mid-winter drought.  A thicker slab overlays this layer in areas that have received more wind-affect and higher snow totals.  A dense slab makes triggering the weak layer lurking below more difficult. If you do end up triggering this layer, it will likely propagate around terrain features and become an unsurvivable avalanche. These sleeping giants are trying to rest after two large storm cycles - don’t wake them up.
  • Sunny slopes facing SW-S-SE-W have a thinner slab sitting on top of a melt-freeze crust.  Since these slabs are usually closer to the surface than their north-facing counterparts, it's going to be easier to trigger these slides. 
  • Cornices have grown to monstrous sizes in recent weeks. These beasts sag and deform during warm temperatures and additional snow and wind loading events, eventually detaching from the ridges they cling to. Cornices that fail can effectively trigger the weak layers described above in the persistent slab problem.  A group yesterday proved that this is possible (observation). 
  • If the sun makes an appearance in between passing snow showers,  pay attention to if the snow is becoming mussy or if slopes above you have roller balls coming down. This time of year, the sun doesn't have to be out for too long to warm up the snow. These wet slides can also be effective triggers for persistent slabs.

The important take-home message is most of these avalanches will be big enough to bury you. Depending on the aspect, some will be very large avalanches that are unsurvivable. Have a conservative plan for entering the backcountry and stick to it. 

Regioni coperte