Lawinenlagebericht

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 7 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

The combination of fresh snow and wind created wind drifts in exposed, upper elevation terrain. Although small, they may be triggered by the weight of a skier or rider.  As the sun warms up the snow surface, expect to see fast-moving loose snow avalanches in steeper, rocky terrain. It'd be a stroke of bad luck, but triggering an avalanche on weak layers buried 4-6 feet deep remains a possibility on very steep, rocky, wind-affected slopes at upper elevations. 

Lawinenprobleme

  • Wind Slabs

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

    The weak storm that drew to a close yesterday brought 6-12" of low-density snow to this zone. Light to moderate winds blowing out of the W-NW-N during and after the storm moved this snow around in exposed upper elevation terrain. This snow was deposited in the form of wind drifts (slabs) in locations where the terrain forces the wind to slow down a bit and drop the snow it is carrying. I like to think about it this way: when you're up high in the mountains looking for a spot to duck out of the wind for a snack, you're likely to choose a place where the wind is building slabs (below ridgelines and along mid-slope terrain features like gullies and rocky ribs). 

    The new snow fell on a variety of surfaces, most of which were pretty firm, such as older hard slabs and slick, icy crusts. With a bit of time to bond, these recent slabs aren't likely to be particularly touchy today, but if you are able to trigger one it will pick up speed quickly as it travels downhill over these firm older surfaces. Look for signs of wind affected snow, such as dune-like drifts and ripples on the snow surface to help you identify areas of drifted snow. These surface textures can be large or small.

    ADDITIONAL DISCUSSIONTriggering a 4-6 foot thick persistent slab avalanche has become very unlikely. It would take a dose of very bad luck, but it may be possible to trigger one of these monsters in very steep (over 35 degrees), wind-swept, alpine terrain.  

  • Loose Wet

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

    Today will be the first full day of sunshine in this zone since the storm tapered out. With plenty of new snow sitting around, we're likely to see some small, loose snow avalanches. Cold temperatures should mute the impacts of this problem, but won't shut it down entirely. On slopes on the southern half of the compass, those that directly face the sun, the snow surface will warm as the day progresses. This warming is more pronounced where rocks and trees are also being warmed by the sun and radiating out that energy into the adjacent snow. Chunks of snow will melt off rocks and trees, fall into the snow, and start loose snow sluffs that gain momentum as they travel downhill.

    These types of slides are particularly common in the Sawtooths due to the abundance of steep and rocky terrain there. And, thanks to the firm surfaces that the new snow is resting on,  these sluffs will quickly pick up speed as they travel downslope over these surfaces. This problem will follow the sun around the compass throughout the day - starting on SE-facing slopes and migrating around to W-facing slopes. If you're seeing small balls of snow rolling downslope, or if the snow surface is starting to feel moist and stick to your skins, you might think about looking for a more shaded aspect to recreate on.

Avalanche Discussion

New snow problems are the name of the game in our northern zones today. The weak storm that exited the area overnight left us with a fresh coat of paint on the mountains, a welcome sight. The problems that you are most likely to encounter today both stem from this new snow. We've spent so much of the winter worrying about persistent weak layers in the snowpack, it can be easy to forget that these new snow issues are hazardous as well. Let's have a quick review:

Wind Slabs: During and after storm events, the wind transports freshly fallen snow and packs it into slabs. These slabs are touchiest immediately after they are deposited and become less hazardous as time passes.  The simplest way to manage this problem is to look for areas of wind drifted snow and avoid them where you find them. Fortunately, if we are looking for good powder skiing we are probably doing this already. If you are skiing through low-density powder, the type where you hardly have to make any effort to turn, you are likely doing a great job avoiding these slabs. I suspect this is the type of skiing or riding that you are looking for today.

Loose Snow: Loose snow avalanches are typically divided into dry and wet categories, but there are a hundred shades of grey between these two. Today we are likely to see slides that exhibit properties of both dry and wet loose avalanches. If you are skiing or riding in very steep terrain that faces away from the sun you may be able to trigger the dry variety of these. These slides aren't likely to be occurring naturally today. As you wrap around to the south half of the compass, sluffs that start because the sun is warming the snow surface but end up picking up dry snow underneath as they travel downslope are also possible. Today, both natural and human triggered avalanches of this nature are on the table.

Remember that even though both of these problems are more "manageable" than persistent slab avalanche problems, they can still have high consequences because of the terrain where you are likely to find them. If you get caught in a small slide and get carried down through rocks and cliffs, it doesn't really matter if the avalanche is large enough to bury you or not. 

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