Bollettino valanghe

Tetons

Bridger-Teton Avalanche Center
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Pericolo valanghe

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

In sintesi

You can trigger an avalanche on steep slopes with over a foot of recent snow that has not bonded well to the old surface. Though less likely, it remains possible to trigger a larger avalanche breaking on deeper weak snow, particularly in rocky or wind-loaded areas. These slides would be large and take out most of the winter's snowpack. Continued and careful snowpack evaluation and terrain selection will be important today. 

Problemi valanghivi

  • 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 and/or rocky 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 greatly 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.  

     

  • Wind Slabs

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

    Winds have built 1-3’ thick slabs in exposed upper-elevation terrain. New snow and wind equal weight on various weak layers in the snowpack. This stress is amplified in areas where dense, thick wind slabs have formed during recent strong winds. Smaller wind slab avalanches have the potential to step down to more deeply buried weak layers. This could result in a larger avalanche, which is why they are a secondary concern to the problem above, but still something to watch out for while moving in the mountains today. Drifted snow deeper than 8” is a red flag. 

    (2/18/2024)

    This large avalanche likely occurred over the past week mid-storm in the neighboring Greys Zone. The visual ripples in the snow illustrate where some areas saw more wind, and any drifted or winded snow holds a higher potential for triggering an avalanche currently. 

     

Avalanche Discussion

At the risk of undermining any notion of expertise you may think I possess, I've made plenty of bad decisions in avalanche terrain. I'm eternally skeptical of myself. Not to a paralyzing point, but I think about how I think about everything a lot. We are all fallible. The current avalanche scenario has very low feedback and is variable across locations in this zone. You may not receive any signs a slope is unstable, even after multiple tracks on a slope.  How else does one receive feedback when the environment doesn't provide it? Digging and probing will add some data points to your slope-by-slope feedback. With any snowpack, it's very important to recognize when you are dealing with a more complex problem than we as humans can typically fully understand. Hopefully, we’ll have more evidence to pull from after this series of small storms and clearings. I say “hopefully” because we still see such a small portion of a mountain range and what has avalanched or not for feedback in any given cycle. Pad any uncertainty you have today by building a wide buffer zone for error in your travel practices. Remember that slopes with the softest snow conditions that make riding more fun are also the locations where the above two problems are most commonly found. 

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