Lawinenlagebericht

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
2 · Mässig
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 5 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Isolated wind drifts 12-16" thick were reactive to the weight of a person yesterday and will behave similarly today. Be aware of the consequences of being caught and carried by an avalanche in the terrain that you are in. Continue to use extra caution on very steep, rocky, wind-affected slopes.  At lower and middle elevations, triggering a large avalanche is unlikely. 

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Yesterday, at upper elevations in this zone, I found wind slabs up to 12-16" thick that were reactive to my weight. Have a look at the video I made describing them. The wind continued to blow overnight, which helped these slabs grown in size and distribution. Today, these slabs will be plenty large to knock you off your feet and take you for an unpleasant ride. In some areas they may be large enough to bury you. Look for and avoid areas with evidence of recent wind loading.  Dunes, drifts, and pillowed snow textures are all great indicators that the wind has been at work. As overall snowpack stability improves in this area and we move into steeper, rockier terrain, we will be well-served to remember that even small slabs can have high consequences.

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    2–3

    We've been plagued by persistent weak layers the entire season. First by early-season facets near the ground, then by weak layers that were buried in late-January and February. These weak layers still exist on most slopes, but observations from across the forecast area indicate that triggering a persistent slab avalanche is unlikely.

    Even though triggering a persistent slab avalanche is unlikely, that's not the same as impossible. There's still a small chance of triggering a persistent slab avalanche on very steep, rocky, wind-affected slopes, particularly those that face the sun. Terrain like this is most common at upper elevations and especially in the alpine. Take a look at the photo at right/above that I snapped last week of an avalanche that occurred in exactly this sort of terrain in this zone.

    (3/3/2021) Crown of a large slab avalanche in the Sawtooth Mountains. This slide failed on a S/SE facing slope at 8,800'

Avalanche Discussion

AVALANCHE DANGER

The avalanche danger scale is an imperfect tool. There, I said it. But the shortcomings of the scale aren't necessarily a problem related to the danger scale itself, they are natural outgrowths of the problem at hand. When we rate the avalanche danger for a given zone we are trying to describe the wide range of snow and avalanche conditions you will encounter over a roughly 800 square mile area, using just a single word. When you think about it this way it should come as no surprise that the danger scale has its shortcomings.

As avalanche forecasters, we use the avalanche danger scale because it is a way to quickly convey information about the backcountry snowpack to our users. But, it isn't the only tool we use. The avalanche problems give you an idea what type of issue you should be thinking about, and the graphics next to the problem help you understand where the problem is most likely. Personally, I spend the great majority of my forecasting time writing text that is intended to help you understand what you might find out there. So, while the danger scale is a good starting point, it shouldn't be your end point. 

One thing that isn't communicated well with the danger scale is the element of uncertainty or unpredictability that exists in an area. This can be a very important piece of information for a person traveling in the backcountry. As we see danger dropping to LOW in almost our entire area it is easy to find yourself thinking that conditions are the same everywhere. But, this isn't the case. There are places in our forecast area where I just can't convince myself are a good idea to go right now. This isn't because I think triggering an avalanche is much more likely there, its because there is a level of unpredictability that I'm just not comfortable with. The thought of entering big, open bowls peppered with rocks in the alpine terrain of the Boulder, White Cloud, and Pioneer Mountains makes the hair on the back of my neck stand up.

What is it about this terrain that is so concerning? Thanks to a combination of wind and a lack of snowfall, the snowpack in these areas has stayed relatively thin all season long. A dense, stiff slab is sitting on top of the weak snow that has plagued us all season, and thin areas in the snowpack allow a skier or rider better access to this weak snow. These aren't the only places this combination exists, but they are the first that come to mind. If you find yourself looking down past your ski tips at this type of terrain today I challenge you to prove to yourself why entering that terrain is a good idea. If you feel comfortable with your knowledge of how the snowpack will behave, by all means, have at it. The early season snow in our area has behaved unpredictably all season long, creating large avalanches with small loads and producing slides many days after loading. For me, this unpredictably has me playing on the conservative side of things in areas with this sort of snowpack. 

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