Lawinenlagebericht

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
Auf der Karte ansehen

Lawinengefahr

Mon
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
Open full map
Veraltet — dieser Lagebericht ist 3 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Slabs of wind drifted snow in upper elevation terrain will be sensitive to your weight today. Weak layers buried underneath dense, 2-4 foot thick slabs of snow can produce much larger, more destructive avalanches. You aren't likely to experience signs of instability with these deeper weak layers—the first sign may be the large avalanche you trigger. These slides can be triggered a distance away from the slope that avalanches. Choose simple terrain free of terrain traps to reduce your risk.

Lawinenprobleme

  • Persistent Slabs

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

    Layers of weak snow are buried beneath very dense, 2-4+ foot thick slabs. Triggering an avalanche on these layers is not likely, but the outcome of doing so would be catastrophic. Watch the video to the right/above to get a better feel for this problem.

    These weak layers produced a set of historic avalanches in the past two weeks (map, list). Aside from the crowns and debris from these avalanches, you aren't likely to encounter signs of instability from these buried weak layers today. If you don't dig down, the snow will "feel good". If you want to see this weak snow for yourself, pull out your shovel. You'll find crust+facet combinations on sunny slopes and small facets on shaded slopes. But don't expect to gain a lot of information by digging; snowpack tests are unreliable for weak layers underneath thick, dense slabs of snow.

    Tracks on a slope are not an indication of stability. Avalanches may be triggered after many skiers or riders have traversed a slope. The first sign of instability may be the large, destructive avalanche you trigger. These slides may break much wider and much further above you on the slope than you expect. They can be triggered remotely—from gentler terrain above, below, and to the sides of steep slopes.

    These types of avalanches are hard to deal with. The only way to eliminate your risk of encountering one of these beasts completely is to avoid avalanche terrain and terrain exposed to hazard from above. I know, that's not satisfying to hear. You can reduce your risk by avoiding slopes steeper than about 35 degrees—especially large avalanche paths and those with ugly consequences if you are caught in a slide. Remember that even small slopes can carry high consequences when we are dealing with very dense slabs.

  • Wind Slabs

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

    The past few days have brought an ongoing trickle of snow. Ridgetop winds have been blowing out of the NW, building a few generations of wind slabs. A bump in wind speeds and additional snow falling this afternoon will help these slabs to grow in size and to remain reactive. These slabs are building on a variety of snow surfaces, including facets and crusts with facets on top. You'll be most likely to find these slabs near ridgelines and on the sides of mid-slope terrain features like gullies and ribs. In the steep terrain of the Sawtooths, slabs commonly form in cirques below large cliff bands and on the aprons below couloirs.  

    Pay attention to how much new snow you are finding and to the snow you are moving through. If it is becoming deeper and denser you are likely moving through a wind slab. Cracks shooting out from your skis or machine are clear indicators that the slab you've found is unstable. These slabs are building on top of some crusts and facets that developed over the past week. These weak layers may make today's slabs more sensitive than you would normally expect. I found small, sensitive wind slabs in this Zone on both of the last two days. 

    Look for textures on the surface (drifts, dunes, ripples, pillows, etc.) that indicate the wind has been at work. You'll be most likely to find these slabs near ridgelines and on the sides of mid-slope terrain features like gullies and ribs. In the steep terrain of the Sawtooths, slabs commonly form in cirques below large cliff bands and on the aprons below couloirs.  Smaller triggered slides can be effective triggers for the weak layers described in the Persistent Slab problem above.

    ADDITIONAL DISCUSSION: Expect the new snow to produce small, loose snow avalanches on very steep slopes. These small slides will be easy to trigger and may run fast and far, particularly where the new snow is sitting on a crust.

Avalanche Discussion

You will be faced with two very different categories of avalanche hazards today. At the surface, you'll find fresh wind slabs that will be reactive to your weight and loose snow avalanches that will be easy to trigger. These types of problems are relatively easy to identify and manage. Further down in the snowpack, you'll find the weak layers that produced the impressive, widespread, and in places historic avalanche cycles earlier in the month.  Identifying which slopes may avalanche or where you need to be on a slope to produce an avalanche is essentially impossible. The only surefire management strategy for this type of problem is avoidance.

If you're feeling like you have to enter big, steep avalanche terrain today, I recommend spending some time contemplating the consequences of triggering an avalanche on the weak layers buried in our snowpack. It can be hard to wrap one's head around the destructive power of these meaty slab avalanches. Fortunately, mother nature has already done the work of imagining for us. Find a large crown and look at the debris below. There are large piles of debris littering our mountains, you probably won't have to look hard to find one. These are the types of avalanches that are on the table. The weak layers are deeply buried and impacting them with our weight is not an easy task. It's more likely than not that you won't trigger a massive avalanche on the slope you are planning on riding or skiing. Unfortunately, if the dice come up snake eyes and you do trigger one of these slides, there is a good chance that you won't survive. 

Dealing with low likelihood/high consequence problems is incredibly frustrating. It is late March and we are all ready for some bigger terrain, but that terrain isn't ready for us. Our travels in the mountains are driven by the snowpack, not the calendar. We've made it to spring, but the snowpack is still wearing her winter hat. When you head into the mountains today, you'll find a dry, cold snowpack complete with weak layers buried underneath meaty slabs of snow. With our snowpack behaving like winter we are well served to follow her lead, she is the boss.

Watch Ethan's Weekend Update to get caught up on what happened last week and for a sense of where we are headed this weekend.

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