Lawinenlagebericht

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

Conditions are dangerous. You're most likely to trigger avalanches on slopes where the wind has formed drifts or stiffened the snow surface—even at lower elevations. While slides are most likely where the wind deposited snow, they could also occur in steep wind-sheltered terrain. Avalanches may be triggered remotely—from gentler terrain above, below, and to the sides of steep slopes.

Lawinenprobleme

  • Persistent Slabs

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

    You could trigger a 1.5-3' thick persistent slab avalanche on steep slopes. Persistent weak layers (sugary facets, surface hoar, or crusts) exist on most aspects and elevations. The widespread nature of this problem is unusual. Triggering a large, dangerous avalanche is likely on a variety of slopes including lower elevations and in terrain sheltered from the wind.

    Wind and snow over the past few days created fresh wind slabs (see below). The added weight is stressing the buried weak layers, especially at middle and upper elevations where thicker, heavy wind drifts are more common. You may experience snowpack collapsing and/or cracking while traveling. These red flags are obvious signs of instability. Remember that you could trigger slides remotely—from gentler terrain above, below, and to the sides of steep slopes. These avalanches may break wider than expected or higher on the slope above you. 

    Unfortunately, avoiding slopes steep enough to slide is the only way to effectively manage this problem. I'll be sticking to lower-angled, wind-sheltered slopes to reduce my risk.

    (12/13/2022) Numerous large avalanches were observed in the Lake Ck Drainage N of Ketchum. This large avalanche is on a NW-facing slope at 8,400' near Triple Pk.

  • Wind Slabs

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

    Snow and wind over the last few days built sensitive slabs on many slopes (video). These slabs will be thicker and more widespread at middle and upper elevations but yesterday's extreme wind event also built slabs at low elevations right down to the valley bottom. Fresh drifts sit atop a weak surface of crusts, facets, and surface hoar. 

    Yesterday near Cape Horn, Chris described a snow plume launching off of Copper Mtn the likes of which he'd never seen. In the Boulders, a set of impressive wind slab avalanches released in Eagle Ck (above/right), cascading nearly 2,000 vertical feet before piling debris in the gully below. Skiers triggered wind slab avalanches in Indian Ck and Quigley Canyon. Dozens of natural wind slab avalanches released on a variety of aspects at middle and low elevations from the foothills north of Fairfield to the mountains around Hailey. 

    Today, you should be looking for and avoiding obviously wind-loaded terrain. Yesterday's unusually strong wind built slabs in unusual places. You may find them far below ridgelines, on the sides of gullies, and near prominent terrain features in normally sheltered areas. I'd assume any drift you encounter will be touchy to your weight until proven otherwise. Smaller wind slab avalanches could "step down", triggering the large persistent slab avalanches described above.

    (12/21/2022) Skiers remotely triggered this avalanche on an E-facing slope at 5,500' in Quigley Canyon.

    Photo: C. Grover

Avalanche Discussion

UNUSUAL

I found myself writing the word unusual in both of our problem descriptions. In November, we developed an unusually weak and widespread weak layer that sits at the base of the snowpack. Yesterday, we experienced unusually strong wind. Upper-elevation wind speeds >30mph were commonplace and Peak 2 in the Soldiers recorded multiple gusts topping 100mph!

Safe backcountry travel depends a lot on pattern recognition and our ability to match the expected avalanche problems with terrain that's appropriate for the conditions. Sometimes, however, we observe weather or snowpack setups that are outside of our experience. It's in these times that our well-worn skin tracks and rules-of-thumb need to be re-examined. Yesterday's wind event was one of those days. I live at the base of Carbonate and have only seen the S-face avalanche twice (yesterday included) in the last 8 years. Skiers triggering avalanches just off of the valley bottom is not the norm here, but it's what we can expect again today. 

Today, you could trigger hard slab avalanches on many slopes including more isolated terrain near the valley bottom. Rather than taking your "standard route", look around you for obvious signs of recent wind affect or natural avalanches. Recent slides provide a blueprint for suspect terrain that we should be steering clear of again today.

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