Lawinenlagebericht

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
Auf der Karte ansehen

Lawinengefahr

Tue
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
Open full map
Veraltet — dieser Lagebericht ist 6 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

A slow trickle of new and windblown snow is creating sensitive wind drifts and loading buried weak layers, particularly in the western portion of this zone (Dollarhide Summit to the Soldier Mountains). Triggering an avalanche 1-3 feet deep is possible, especially on steep, upper elevation slopes. You can dramatically reduce your risk of getting caught in an avalanche by sticking to wind-sheltered, low- and mid-elevation terrain.

Lawinenprobleme

  • Persistent Slabs

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

    There are two main persistent weak layers in our snowpack:

    1. Depth hoar exists near the ground on all aspects (excepting low elevation slopes that are snow-free). This is the snow that we've been talking about all season long and seem to be destined to talk about for the remainder of the season.
    2. In the middle of the snowpack are several interfaces that have produced both avalanches and unstable test results in recent days. In this zone, these layers appear to be worst where they are accompanied by a crust.

    I went looking for these problems in this zone yesterday and I found both of them. Near Dollarhide summit, I dug snowpits on shaded slopes and those that face the sun and got poor snowpack test results in both locations. You can read my observation here, and see a photo of those snowpits here. As I continued upwards, I found a large, natural avalanche that appeared to have failed on a crust before stepping down to weak snow near the ground within the last few days. This slide was located in exactly the type of terrain that you should be avoiding if you want to reduce your risk of encountering a slide today: wind-affected slopes steeper than about 35 degrees. You can greatly reduce your risk of triggering a large persistent slab avalanche by sticking to middle elevation slopes that are sheltered from the wind.

    (2/12/2021) This avalanche was triggered by a rider NE of Wells Summit in the Soldier & Wood River Valley zone. The slide broke around 40' wide and carried the rider about 100 yards. A section of the cornice also released in the slide.

  • Wind Slabs

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

    In the past few days, the combination of a slow trickle of snowfall and moderate winds have been built slabs in exposed terrain. New Dollarhide Summit yesterday, I watched the wind moving plenty of snow and encountered recent thin, stiff drifts as I climbed in elevation. On Saturday, Soldier Mountain Cat Ski guides remotely-triggered a wind slab avalanche that broke 1.5' deep (photo above/right).

    The wind will continue to blow today, picking up in speed as the day passes. Triggering an avalanche such as the one pictured will remain a possibility. Wind slabs may be found near ridgelines or mid-slope in exposed terrain. These slabs are hazardous in their own right but they are also adding stress to the weak layers buried in the snowpack (described above). Any wind slab you trigger could step down to these deeper layers, producing a much larger and more dangerous avalanche. 

    (2/20/2021) Ski guides remotely-triggered this wind slab avalanche yesterday on Peak 2 in the Soldiers while doing mitigation work. It broke 1.5' deep. Photo courtesy Soldier Mountain Cat Ski.

Avalanche Discussion

BIRTH OF A WEAK LAYER

If you've made it this far down the page you are well aware that we have layers of weak snow in our snowpack. In fact, we have several of them. You may find yourself wondering, where do weak layers come from? Well, they don't just spontaneously appear in the snowpack. Most often, they develop at the surface and are then buried by the next round of snowfall. 

When we are out in the mountains we are generally looking for the best surface conditions that we find. After all, skiing and riding powder is more fun than skiing and riding breakable crust. If you've been out in the past few days, looking for powder, you have probably noticed that there is a crust on top of the snow on slopes that face the sun. Depending on the conditions that they form in and how they are buried, crusts can make for long-lived weak layers. In fact, the combination of a sun crust with some small, weak facets on top was the weak layer responsible for the avalanche that resulted in the death of a rider in Smiley Creek on Friday. 

As we look forward to more snowfall overnight and another shot later in the week we can think about the surfaces that will be buried. If you want some homework, spend a bit of time mentally mapping where you are finding crusts today. If the crusts that we are burying this week end up being persistent weak layers you will have some sense where they are located and how to avoid them. Of course, weak layers can form without a crust too... It's never simple out there.

Abgedeckte Regionen