Avalanche forecast

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
View on map

Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
Open full map
Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Large human-triggered avalanches are possible, thanks to the layers of weak snow buried in the snowpack. Recently formed wind drifts and slabs are likely to be small but may be sensitive to your weight. You can reduce your risk today by steering clear of slopes that have been affected by recent winds.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    Several weak layers exist in the snowpack. You're most likely to trigger avalanches on weak layers that are closer to the surface, but slides on deeper weak layers remain a real possibility here. The distribution, sensitivity, and depth of these layers vary across the zone and from slope to slope.

    • Surface hoar is buried 1-1.5' deep on many shady (E-N-W) slopes. In this zone, 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

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Today, you'll find a patchwork of wind slabs at and near the surface. A multi-day wind event this week constructed stiff, dense wind slabs. Yesterday's snowfall+wind built another batch of softer slabs on top of the older slabs, and similar slabs will continue to form today. Wind slabs will be variably reactive, and the most recent slabs are likely to be the most sensitive to your weight. Slabs are most likely in upper elevation terrain, though you may find them in exposed middle elevation terrain as well, thanks to the strength of the wind.

    Multiple wind slab avalanches were observed in this Zone this week (photo at right/above). Though relatively small, these slides picked up speed and snow as they traveled downslope. Be on the lookout for fresh slabs—if the snow you are moving through becomes deeper or more dense you've likely found one. Cracks shooting out from your skis or sled are a clear sign that you've found an unstable slab. Small slides can pile up debris deeply in terrain traps like road cuts or creek beds (photo here). Consider the consequences of being knocked off your feet and sent downslope in the terrain you are in.

    (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

Early season storms brought roughly equal helpings of snow across our forecast area. This helped to build a snowpack that was somewhat homogenous across the region. However, over the past month, snowfall has favored our northern and western mountains and we've seen a significant divergence in the character of our snowpacks. In a broad sense, you can lump them into two categories: shallow and deep. The Soldier and Wood River Valley Forecast Zone straddles the boundary between these categories. 

On the eastern side of this zone and in the mountains above the Wood River Valley, the snowpack remains thin (around 3' deep) and much of the snowpack is faceting. When this happens, the slabs in the snowpack lose strength and triggering an avalanche on buried weak layers becomes more difficult. Here, you are much more likely to trigger a slide where recent winds have built slabs on top of the weak snowpack.

On the western side of this zone (Dollarhide and west to the Soldiers), the snowpack is thicker (4-5' deep) and the slabs over the weak layers remain intact. Weak layers buried in November and December are resting underneath very dense, heavy slabs of snow. Impacting these weak layers with our weight is unlikely, though not impossible. However, the prominent weak layer that was buried in January is sitting under a 1.5-2 foot thick slab and impacting it with our weight remains a real possibility. This layer has proven itself to be at its worst on shaded slopes (those on the northern half of the compass), where standing surface hoar can be found under this dense slab. However, a pattern of unstable snowpack test scores on sunnier slopes—where a crust is accompanied by facets and some surface hoar—are worth keeping in mind as you travel through the mountains. 

With prominent weak layers in the snowpack, fresh wind slabs at the surface, and an ongoing trickle of snowfall, the decision to choose simpler terrain today is an easy one. The consequences of triggering avalanches can vary significantly. Triggering a small slide in terrain free of rocks and trees and terrain traps is much safer than triggering a slide in extreme, rocky, treed terrain with a terrain trap at the bottom. Spend some time thinking about snowpack complexity and the consequences of being caught in a slide as you are choosing your terrain for the day.

Regions covered