Avalanche forecast

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Sawtooth Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

You could 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.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    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 is now buried beneath a dense slab that's 3' thick or more on most mid to upper elevation shady slopes. The weak layer in this zone is becoming more deeply buried, making it more difficult to impact with our weight. As a result, you're likely to experience less obvious signs of instability, but the flip side is any slide you trigger is likely to be a big one.  

    While the stability is (very) slowly improving, most observers are still reporting poor snowpack test scores. We're only about four days out from the big storm, and dribs and drabs of snowfall along with periods of wind transport are not giving the snowpack the break it needs. In short, the snowpack needs more time to pull it together.

    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 safer avalanche conditions on low and middle elevation slopes that are southerly-facing and hence lack the old October snow.

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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