Avalanche forecast

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Highlights

Snowfall and wind have built slabs in exposed, upper elevation terrain. Additional wind and snow today will help these slabs to grow in thickness and distribution. They may be sensitive to your weight, particularly where they rest on weak surfaces such as facets and crusts. Look for signs of recent wind loading and unstable slabs, such as cracks shooting from your skis or board. Rain on dry snow at lower elevations will increase the threat of loose snow avalanches as the day progresses. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    The combination of fresh snow and wind built slabs in upper elevation terrain this weekend. Yesterday, on a recreational ski day in the Boulder Mountains, I was able to intentionally trigger one of these slabs on a steep slope (photo at right). The slide started small, but picked up speed quickly as it ran downslope. Triggering a similar slab remains a possibility today, particularly where they rest on weak, faceted snow and slick, icy crusts.

    An additional 1-2 inches of snow will fall today, accompanied by light winds with moderate gusts. These winds are right at the threshold for building wind slabs. If winds are lighter than forecast they won't be able to move much snow, but if they are a bit stronger you will see slabs build quickly near ridgelines and mid-slope terrain features like ribs and gullies. Look for evidence of wind drifting such as dune-like drifts and ripples on the snow surface and fresh cornices along ridgelines. Cracks shooting out from your skis or board are a sure sign that you've found a sensitive wind drift. 

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Warm air temperatures and rain at lower elevations will increase the hazard of wet loose avalanches today. These slides will be most likely on slopes steeper than about 35 degrees that face NE-N-NW. In these areas, dry snow will become wet for the first time. Slides will start at a point and fan out as they travel downhill. Many slopes at lower elevations aren't steep enough for this type of problem. Unfortunately, quite a few of the ones that are steep enough sit above terrain traps, like gullies and creek bottoms. In these areas, avalanche debris from even a small slide can pile up deeply enough to bury you. 

Avalanche Discussion

The avalanche danger scale is a five-step scale that avalanche forecasters use to communicate information about the avalanche hazards you might encounter in the backcountry. Of course, the world doesn't fit neatly into five boxes. There are innumerable shades of gray and subtleties that can't be perfectly communicated with a simplified scale.  Today, the avalanche danger is MODERATE and human triggered avalanches are possible across our forecast area. However, the type of slide that you might trigger varies significantly. Let's take a quick look:

  • Pioneer Mountains and Little Wood drainage: The southeastern corner of our forecast area got clipped by a significant stream of water this weekend. While many of our other areas picked up just a few inches of snow, The Swede Peak SNOTEL recorded 15 inches of snow and 1.3 inches of SWE (snow water equivalent). Here, a very weak snowpack was stressed with a significant load for the first time this season and numerous large, natural persistent slab avalanches occurred. These types of slides can be triggered remotely, including from the bottom of an avalanche path. Dealing with this problem involves building wide safety margins into your travel plans.
  • Sawtooth, Smoky, White Cloud, and Boulder Mountains: 2-6 inches of snow fell in these mountains this weekend, and a few more will fall today. The wind built small slabs out of this new snow in upper elevation terrain exposed to the wind. 

Think about how differently your travel practices need to be to manage these problems. A "simple" wind slab problem creates hazards that are somewhat predictable and avoidable. If you choose to enter avalanche terrain with this type of problem you know what to look for and avoid (steep, wind-loaded slopes). However, a persistent slab problem is a different beast entirely. If you are trying to avoid the hazard posed by one of these beasts you need to look at a significant chunk of terrain as being "off-limits". In both cases, triggering an avalanche is possible, but the type of slide and the way you deal with the hazard are very different.

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