Lawinenlagebericht

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
Auf der Karte ansehen

Lawinengefahr

Sat
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
Open full map
Veraltet — dieser Lagebericht ist 4 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Triggering a large avalanche remains a possibility—primarily in wind-affected terrain. In these areas, a dense slab may exist atop buried weak layers. To reduce your risk, avoid slopes with evidence of wind, such as fresh drifts or a stiffer snow surface that supports your skis or sled.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2.5

    You could trigger a large persistent slab avalanche. You're most likely to find trouble in recently wind-drifted terrain. If you find a healthy, fresh slab, you can assume it's resting on one or more persistent weak layers. The distribution, sensitivity, and depth of these layers are highly variable, leading to a complex snowpack. Here are some patterns to be aware of:

    • Surface hoar is buried 1-1.5' deep on many shady (E-N-W) slopes. Observers continue to find this layer in snowpits, but snowpack tests show improvement. This surface hoar layer is most problematic where recent wind loading has created a stiffer slab in the upper snowpack.
    • Older weak layers, including crusts and/or facets, and occasionally surface hoar, exist deeper in the snowpack. These are buried beneath dense, 2-4' thick slabs—making them difficult to trigger but capable of producing very dangerous avalanches. While triggering them is unlikely, it can't be ruled out in rocky, wind-affected alpine terrain. This recent persistent slab avalanche in the Pioneer Mountains exemplifies the problem (above/right, details). Slopes like these have variable snow depths, with thinner areas of the snowpack that allow us to impact deeper weak layers.

    Overlapping, variable weak layers make conditions less predictable. To reduce your risk, avoid slopes greater than about 35 degrees where the wind has shaped the snowpack. You can recognize wind-affected areas by stiffer or harder snow that is more supportive of your skis or machine and surface texture such as ripples, waves, or dunes.

    (1/24/2023) This recent large avalanche occurred on the shoulder of Duncan Ridge in the Pioneer Mountains. It appears to be a heavily wind-loaded slope that broke on a persistent weak layer. A smaller wind slab avalanche is visible further right in the image. 10,100', WSW.

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–1.5

    Expect to find hard slabs in areas exposed to the wind. Yesterday in the E Fork of the Big Wood, skiers experienced multiple collapses and observed cracking in freshly formed wind drifts. Wednesday near Bellevue, JP observed a wind slab avalanche in a cross-loaded gully (details). Tuesday, Ben observed a similar natural slide near the Hyndman Ck trailhead (above/right). 

    You're most likely to encounter a sensitive wind slab at upper elevations, although recent strong to extreme N and NW wind may have formed small slabs on some middle and lower elevation slopes. When strong winds blow older snow around, they tend to form wind slabs that are hard and dense. They can often have a "chalky" appearance (photo). They can feel hollow or drum-like, which indicates that they are sitting atop weaker snow and should be avoided when on a steep slope.

    While most of the wind slabs we've seen have been fairly small, they can easily knock you off your feet, strain you through trees or bury you in a depression (photo). 

    (1/24/2023) This small wind slab avalanche occurred recently above the Hyndman Creek trailhead, likely as a result of the N-NW winds. As the avalanche moved downhill, it appears to have entrained loose surface snow that is becoming faceted, weak, and sugary. 7500', ESE.

Avalanche Discussion

The avalanche danger is MODERATE across the forecast area. At first glance, avalanche conditions may look similar, but there are variable and divergent conditions across our region. No two MODERATE dangers are alike, and we've arrived at this danger level for different reasons. If you recreate in multiple portions of our forecast area, all of this can be hard to keep track of. To simplify matters a bit, I think it's helpful to mentally separate the deeper snowpacks of the northern and western mountains from the shallower snowpacks of the southern and eastern mountains:

  • The snowpacks in the Sawtooths & W Smokys and Banner Summit zones are more uniformly deep. The deeper snow is advantageous, as it helps to reduce the odds of triggering an avalanche on deeper weak layers buried in December and November. The weight of the overlying slab has helped these older layers to heal, and the stiff snow above them means they're harder to impact. On the flip side, snow since the start of January has buried a weak layer of surface hoar beneath a stout 1.5-2' thick slab on slopes that face E-N-W. The majority of the recent persistent slab avalanches occurred on this layer.
  • The Galena Summit & E Mtns zone has a variable and complex snowpack. The early January surface hoar can be found buried 1-1.5' deep, but it didn't get quite enough load to be a widespread issue. The surface hoar layer remains more problematic where recent or past wind loading has created a stiffer slab in the upper snowpack. Although the surface hoar is less concerning in this zone, the older, more deeply buried weak layers are more worrisome. With a shallower snowpack than further north and west, and more rocky, wind-affected alpine terrain, there are more areas where these weak layers are closer to the surface.
  • The Soldier & Wood River Valley zone can be split in two. In the mountains above Ketchum and Hailey, plenty of weak snow exists but a strong slab is less common. You can avoid most avalanche hazard by staying off of wind-affected slopes where a stiffer snow surface exists. In the western portions of this zone, including the Soldiers and the mountains around Dollarhide Summit, a deeper and much more complex snowpack exists (video). Avalanches occurred in the Soldiers on the early January surface hoar layer, and deeper weak layers may remain a concern in rockier, wind-affected alpine terrain.  

This season has been hard. Plagued with persistent weak layers, it's been an exercise in patience. When I take a step back and think of the big picture, I can't help but see the complexity and variability out there. This gives me much less confidence in choosing a safe place to play. When faced with uncertainty, the prudent move is to stick to inherently safer terrain. This includes slopes less than about 35 degrees and those with more favorable outcomes in case I get surprised.

Abgedeckte Regionen