Bollettino valanghe

Tetons

Bridger-Teton Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Wind continues to craft sensitive slabs with recent snowfall at upper elevations; expect that you will encounter these fresh wind slabs in the terrain you choose today. It would take a stroke of bad luck, but you could also trigger a larger avalanche breaking 3-5 feet deep. You can reduce most of the risk by sticking to lower slope angles and avoiding shallow areas in the snowpack.

Problemi valanghivi

  • Wind Slabs

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

    Yesterday we received multiple observations of skier-triggered avalanches of winded snow ranging 6 inches to 2 feet deep. These were found in exposed upper-elevation terrain and north-facing terrain along gullies and aprons. Expect to find more of these pockets of unstable snow that may break deeper than you expect, and consider the consequences of even a small slide in the terrain you are entering. On southerly aspects, these slabs will be on top of a mix of crusts, and on northerly aspects, a small layer of facets exists at the old snow/recent snow interface. Temperatures are expected to be warmer today, which may affect these slabs as well.  Smaller wind slab avalanches and cornices have the potential to step down to more deeply buried weak layers, resulting in a larger avalanche. Harder, well-connected, drifted snow deeper than 8" is a red flag. 

    (2/19/2024)

    Wind pockets will vary in size and distribution at upper elevations in the Tetons. Choose terrain accordingly, and consider the consequences of even a small slide that rips in an unexpected way. 

  • Persistent Slabs

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

    This zone has persistent weak layers buried 3-5 feet deep on most middle and upper elevation slopes on the north half of the compass. In the last few days, these weak layers have received an increase in loading, both in the form of new snow and wind. Your weight may more easily impact them at middle elevations where the slab is thinner or in rocky areas. It isn't easy to know how thick the snowpack is on a given slope, so consider your terrain choices carefully. Though the likelihood of triggering is trending downward, the consequences have remained the same. You can reduce your risk by:

    1. Choosing moderate slopes with low consequences. With any persistent slab problem, this is our primary line of defense. Safer travel options always exist by sticking to slopes less than ~30 degrees.
    2. Avoiding slopes with shallow areas. The weak layer will be closer to the surface and more easily impacted. Get out a probe and check depths, feel for hard snow over weak snow, & dig to help inform your decisions.
    3. Avoiding terrain where problems #1 and #2 overlap. Triggering a wind slab or cornice significantly increases your objective hazard and will more easily impact deeper layers. 

     

    This large avalanche on No Name likely failed due to a cornice collapse onto the slope below and illustrates that we still have a snowpack capable of producing large avalanches if the right spot is hit.  

     

Avalanche Discussion

Building on yesterday's forecast discussion, I recently spoke with a close friend and fellow snow human about his near-miss accident during Moderate hazard. This occurred several days ago in an area with a sensitive snowpack until fairly recently (similar to here), with a slightly shallower persistent problem. This season has been the season of being on guard for most of the winter across the West, and "MOD" can feel like the floodgates are open. His retelling of the story, feelings about his decisions, and group communication feel all too familiar. They were tired, pressed for time after a long day, and the feature descended had a shallower snowpack than many other areas in the zone. They chose not to look at the snow, committed to the slope though they all felt off about it, and the third skier triggered a large avalanche that flushed the entire path. This serves as a good learning experience by proxy. Again, we are all fallible. When I was younger, I sometimes would find myself relying more on the narratives of others: "They skied it yesterday" or simply coasting on feelings like: "Do I think this will slide?" If my brain's magic eightball conclusion was no, I went for it. This reasoning leaves little room for error since whether a slope will slide is difficult to answer without at least some uncertainty. And it turned out I answered this question wrong a few times. Nowadays, I operate more from where I have uncertainty and a place of: "Would I be totally surprised if this avalanched/avalanched in an unexpected way?" Hedge your decisions in data, take several minutes to pause, regroup your thoughts, check in with your partners, and look at the snowpack beneath your boards or sled.

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