Bollettino valanghe

Tetons

Bridger-Teton Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
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

It is possible to trigger an avalanche 2-5 feet deep in steep, wind loaded terrain at the upper elevations. Watch for thin, rocky areas and wind affected snow as they are most likely to produce a dangerous avalanche. Careful snowpack evaluation will be important today and conservative terrain choices are recommended.

Problemi valanghivi

  • Persistent Slabs

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

    Snowfall and wind over the past two weeks has created thick slabs at the middle and upper elevations. The recently formed slabs are sitting on weak layers of snow that can be found at different depths in the snowpack. Avalanches involving these weak layers could break 3-5 feet deep, or even deeper in some locations. Steep, rocky, and wind loaded terrain on the north half of the compass is most suspect. While the sensitivity of these layers is decreasing, a very large natural avalanche involving buried weak layers occurred in the past 36 hours. This event indicates that the snowpack is still adjusting to the most recent load.

    Approach steep terrain in the upper elevations with suspicion. Extra caution is advised in exposed, wind affected terrain that is punctuated by rocks and cliffs. Obvious signs of instability such as collapsing may not be present. As a result, it is important to make your own stability assessment of a particular slope before committing to steep terrain. If you are unsure about a stability assessment, then defaulting to lower angle terrain is always a good call.

    Persistent slab avalanches south of JHMR that occurred naturally in the past 36 hours.

  • Wind Slabs

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

    Winds have built slabs 2-4’ thick in exposed upper elevation terrain. Wind directions over the past several days have been variable. As a result, slabs could have formed on a wide variety of aspects. Suspect features include exposed ridges, rocky areas, cross loaded terrain, and gullies. A day of warm sunny weather has made these slabs more stubborn in some locations, however, human triggering remains possible. Probing the snowpack for hardness changes (hard over soft) is a good way to identify these slabs.

    Increasing winds out the southwest combined with a few inches of new snow today could build sensitive shallow slabs in upper elevation leeward terrain by the afternoon. Be on the lookout for wind affected snow on the surface that is stiff or drifted. Newly drifted snow that is deeper than 6” is a red flag. A small avalanche that breaks in wind drifted snow could trigger a larger one that fails on deeper weak layers.

    A small wind slab on the east face of Taylor Mountain (2/17). Note the "wavy" wind affected texture below the cliffs.

Avalanche Discussion

The upper elevations of the Tetons have received about 100” of snow containing 7.5” snow water equivalent (SWE) since February 2nd. This is a significant load that is sitting on a poor structure. In the long term, the snow that we have received over the past two weeks is great news for stability. It has helped to bury the concerning weak layers of snow at depths where humans will have a hard time impacting them. Unfortunately, the loading event is too recent to trust the snowpack at the moment. We are only two days out from a significant natural avalanche cycle. The snowpack is still adjusting to the recent loading, despite the signs becoming more difficult to detect. Patience and conservative decision making are recommended while the snowpack adjusts. Building in an extra margin of safety to account for surprises is a good idea today.

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