Bollettino valanghe

Salt River and Wyoming Ranges

Bridger-Teton Avalanche Center
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Pericolo valanghe

Wed
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Periods of intense snowfall and wind will continue the threat of triggering slab avalanches, especially at upper elevations. You're most likely to find trouble where the wind has formed fresh drifts or stiffened the snow. This new snow is also adding additional stress on the weak snow buried deeper in the snowpack. This zone is large and incredibly variable. Cautious route-finding and conservative decision-making are essential, particularly in upper-elevation terrain. 

Problemi valanghivi

  • Wind Slabs

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

    The weight of new snow is adding stress to a variety of weak layers in the snowpack. This stress is amplified in areas where dense, thick, wind slabs formed during recent strong wind. Our most concerning persistent weak layers sit near the middle of the snowpack. An avalanche failing on one of these layers has the potential to be very large, particularly in open and well-connected terrain features.

    Additionally, wind slabs may build today along exposed ridges and in cross-loaded gullies as well as lower on slopes. Cracks shooting from your boards or sled are an obvious sign that you’ve found a sensitive slab. Smaller wind slab avalanches have the potential to step down to more deeply buried weak layers resulting in a large avalanche.

  • Persistent Slabs

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

    The weight of this new snow is adding stress to a variety of weak layers in the snowpack. This stress is amplified in areas where dense wind slabs may form today.  

    Our most concerning persistent weak layers sit near the middle and base of the snowpack. An avalanche failing on one of these layers has the potential to be very large, particularly in open and well-connected terrain features. Persistent weak layers are difficult to deal with. They can produce avalanches many weeks after they are buried and they provide fewer and fewer obvious signs of instability as the days without a significant loading event pass. They can break wider than you might expect and may be triggered remotely, from gentle terrain adjacent to steeper slopes.

    Digging a snowpit in one location may not identify these layers, but will clue you into what the overarching structure at a certain aspect or elevation may look like. Broadly, the snowpack structure is poor here, and use extra caution, even in terrain sheltered from the wind, where weak structure (any harder snow + softer snow underneath it) exists.

    (1/5/2023) Photo: Antonioli

    Persistent slab avalanche in the Wyoming Range. 9500' SE aspect

Avalanche Discussion

Each new storm buries a new interface to think about. Depending on the character of the older snow, the bond at this interface can vary significantly in strength. Generally speaking, as the complexity of the snowpack increases, it becomes more and more difficult to confidently assess the stability of a given slope. You can try to limit some of the uncertainty present when dealing with complex avalanche problems by keeping track of these layers in the areas that you frequent. The challenge this poses is no small task.

In the Greys Zone over the past week, I've found snowpack depths ranging from 12 inches to over 3 feet deep; one sub-zone had widespread melt-freeze crust from a recent clearing above 9,000 feet, even on northerly and shaded aspects, while another held soft, dry snow still even in the lower elevations. I've found buried surface hoar, thick layers of facets in the middle and base of the pack, and also thick crusts at the base of the pack with very little facet development-literally every condition in the book. Microclimate zones exist within each larger range (whether it's the west vs east of the Tetons, the differences along the Continental Divide at Togwotee, or the Salt Range vs Wyoming Range of the Greys), and each is worth getting to know closely if you are frequenting it.  With any snowpack, it's very important to recognize when you are dealing with a problem that is more complex than we as humans can typically fully understand. We can still make our best assessment with all the tools available to us, and our best bet is to always step back if surprised by something. Pad your uncertainty by building healthy margins for error into your travel practices, and tread lightly with rapidly changing snow conditions today.

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