Bollettino valanghe

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Conditions remain dangerous. You are likely to trigger a large avalanche on shady slopes (NW-N-NE-E facing) at upper and middle elevations. In these areas, slides can be triggered remotely—from flatter terrain below, above, and to the sides of steep slopes. Safer conditions exist in south-facing terrain at low and middle elevations.

Problemi valanghivi

  • Persistent Slabs

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

    Where October snow lingered through November's warm temps and dry weather, it turned into a mess of slick crusts and sugary facets. This old snow was buried by last week's Snowmageddon and produced very unstable conditions. Large avalanches (photo, photo) occurred naturally and were also remotely triggered from large distances away (photo). This layer is buried 2-3' deep on most mid to upper elevation shady slopes.

    Several groups in this zone yesterday—ranging from Galena Summit to the Pioneer Mountains—reported continued collapsing of the snowpack.  While we're now several days out from the storm, it's clear that the snowpack needs more time to heal. While we've shaded the problem rose above to depict where you're most likely to trigger an avalanche, any slope harboring old snow (appearing as a mix of facets and/or crusts near the ground) is suspect. The difference between slopes that has old October snow and those that don't is fairly stark (watch video at right/above).

    Folks are finding great sliding and riding, as well as safer avalanche conditions, on low and middle elevation slopes that are southerly-facing and hence lack the old October snow.

    Additional Discussion:Light, low-density snow, and periods of moderate wind over the past few days may have created fresh wind drifts in upper elevation, wind-exposed terrain. I saw two small recent wind slab avalanches (photo) yesterday. These are likely to be isolated, and not particularly touchy, but still worth watching for—especially in alpine terrain.

Avalanche Discussion

Conditions right now are somewhat binary—slopes either have old October snow, or they don't. However, there are a few subtle, but important points to consider:

  1. The pattern of October snow that lingered through the November dry spell varies across the forecast area. Our northern and western mountains had greater early-season snow coverage, as did our higher elevation mountains such as the Pioneers and Boulders. The Wood River Valley had less October snowfall, and it melted on all but the shadiest slopes above about 8000'.
  2. The pattern of October snow coverage is now disguised by last week's storm snow. Many lower elevation slopes have sage and other ground cover poking through, making it clear that the new snow fell on dirt. But as you travel into the middle and upper elevations, it becomes increasingly difficult to discern. With the still-limited snow coverage, we're drawn to slopes with the deepest snowpack—which are also more likely to harbor the old snow.

So what can you do? If you're using the presence or absence of the early season snow as a primary factor in your terrain selection, give yourself a healthy margin of safety. Sticking to due S-facing terrain at low to middle elevations is a fairly safe bet, especially if you can recall whether that slope was bare prior to the recent storm (early-season snow coverage photos anyone?). But veering into SE or SW-facing terrain, or ascending into the upper elevations, may put you in terrain with greater uncertainty. Digging a snowpit on a representative (similar aspect and elevation) but safe slope can also be helpful in determining whether the facet/crust weak layer exists. And sticking to low-angled terrain is always an option—now that the storm snow has settled out, you don't need a steep slope to make turns. Setting clear boundaries for yourself—in terms of aspects, elevations, and slope angles—can help you stay safe and enjoy some great early-season powder!

Catch up on what happened last week in our latest Weekend Update!

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