Avalanche forecast

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Avalanche danger

Wed
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

The combination of new snow and wind has created dangerous avalanche conditions on upper elevation slopes. Triggering a 1-2.5' thick avalanche is likely in upper elevation terrain that is exposed to the wind. These slabs may be able to trigger older generations of wind slabs as they travel downslope, creating a larger avalanche. And while unlikely, we can't rule out the possibility of triggering an unsurvivable, 3-5 foot thick avalanche on very steep, rocky, wind-affected slopes. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Upper elevation terrain in this zone picked up over a foot of new snow yesterday, with an additional 4-6" possible today. Moderate to strong winds blew out of the SW and then NW yesterday. This combination of snow and wind has built 1-2.5' thick wind slabs that will be sensitive to your weight today. Triggering one of these slabs can produce an avalanche large enough to bury a person. Before yesterday's storm, well over a foot of snow had already accumulated in favored portions of this zone, accompanied by moderate winds. These conditions generated an older batch of wind slabs. These older slabs are likely to be less reactive today, but any fresh slab you trigger could "step-down" into these older generations of wind slabs.

    Avoid steep and/or consequential slopes where you see evidence of wind loading—such as a drifted or pillowed appearance, or subtle changes in snow texture. You're most likely to find fresh wind loading along exposed, upper elevation ridglines. In the steep and rocky terrain that is common in the Sawtooths, snow trickling down cliff faces tends to accumulate on the aprons below, forming "spindrift slabs", which may also be sensitive to your weight today.

    ADDITIONAL DISCUSSION:Cloud cover looks to be variable today, with periods of clouds and sun. As we trend towards the spring and the sun climbs higher in the sky the intensity of solar radiation increases by the day. It doesn't take too much sun for the snow surface to melt, creating the possibility of loose snow avalanches in steep terrain. This problem is fairly simple to manage—if the sun comes out be aware of the terrain you are exposed to from above.

    The ongoing snowfall has been accompanied by periods of moderate westerly winds, and you're likely to find fresh wind drifts and slabs along upper elevation ridgelines.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    3

    In this zone, the December facet layer is buried beneath a very dense, 3-4'+ slab. A unique characteristic of this weak layer is that despite having a crushing amount of weight above, it is not getting "squashed" like a more normal layer of facets would.  When a layer is buried this deeply, stability tests are time-consuming and really don't work that well—but don't worry, we did the work for you.

    It would take being in the wrong terrain, as well as a dose of bad luck, to trigger this layer. But if you did trigger a deep slab, you'd need all the luck in the world to survive it. So what's the wrong sort of terrain? Steep (over 35 degrees), rocky, wind-affected, "prime-time" terrain. You can avoid most risk of triggering a deep slab by sticking to sheltered, mid-elevation slopes where a more uniformly deep snowpack exists.

    (2/9/2021) A natural deep slab avalanche on McDonald Peak in the southern Sawtooths. It occurred last Sunday during the ongoing wind event.

Avalanche Discussion

NEW SNOW AND OLD SNOW

Over the past few days we've seen a slow trickle of snowfall across our region. As this new snow has gradually stacked up, we've enjoyed a significant improvement in skiing and riding conditions. The stiff wind slabs and icy crusts that built during the extended wind event are covered up with soft, fluffy powder and I'm not hearing anybody complain about that. From a snow stability and avalanche danger perspective, we've seen our concerns diverge into two sets of issues that we should be thinking about as we travel in the mountains today:

  1. NEW SNOW: The mountains south and east of Galena Summit have picked up 3-10" of new snow in the past few days, while the mountains to the north and east have stacked 18-24". The winds have been at work at upper elevations, generating a few batches of wind slabs over this period. The freshest batch of slabs will be the most sensitive to triggering today, but older slabs shouldn't be ignored. As you travel down into more wind-sheltered middle and lower elevation terrain you will find better riding and skiing conditions in addition to less dangerous avalanche conditions. That sounds like a good place to be! In areas where more snow has accumulated, you may also encounter some loose snow issues today. Dry loose avalanches (sluffs) will be on the menu in steep terrain. And, if the sun comes out for long, expect to see some natural loose snow avalanches initiating on slopes that are being warmed by the sun. 
  2. OLD SNOW: Everything that is going on in the upper portion of the snowpack is taking place on top of a foundation of weak snow. In our northern areas (Banner Summit and Sawtooths) this weak snow is now buried under a 4-6' thick, very dense slab of snow, which has become difficult to impact with the weight of a skier or rider. Further south, where the slab of snow is thinner, this layer is more accessible and the possibility of triggering a slide on this weak snow is much greater. It is easy to forget about this deeper issue when we are focused on the new snow issues and there is great powder skiing and riding to be had. But, unfortunately we are a long ways from being out of the woods on this one.

The snowpack is complex and tricky this season and in order play in the mountains safely we need to give it the respect that it demands. My primary goal is always to return home safely at the end of the day. After all, I can't go powder skiing tomorrow if I don't make it out safe today. Keep it tight my friends, and enjoy the fresh snow!

Regions covered