Avalanche forecast

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Avalanche danger is highest in the eastern portion of this zone—the Little Wood drainage, Pioneer Mtns, and near Bald Mtn—where avalanches are possible even on sheltered slopes. There, 16-20 inches of new snow since the weekend fell on a weak snowpack. Throughout this zone, watch for wind drifts near ridgelines, especially in upper elevation and alpine terrain. If the sun comes out, there is potential for wet loose slides on steep slopes directly facing the sun.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    The southern Pioneer Mtns (including the Little Wood drainage, Mormon Hill, and Swede Peak areas) as well as Bald Mtn near Ketchum, received 16-20” of dense snow since last weekend. This new snow fell on persistent weak layers that formed during the February dry spell and resulted in several large, natural persistent slab avalanches. Some of the slides were hundreds of feet wide (photo to right), failing at the interface between the new snow and the old rotten snow on shadier slopes. Today, you are most likely to trigger a slab avalanche where the wind has affected the snow, but slides large enough to bury people are possible in sheltered terrain too.

    Persistent slab avalanches can break above you, and the 3rd or 4th skier or rider could be the one to find the right/wrong spot to trigger an avalanche. You may be able to trigger slides remotely: from flatter terrain above, below, or to the side of a steep slope. Building in some extra safety margin is the only way to safely "manage" this problem. 

    ADDITIONAL DISCUSSIONIn the Soldier Mtns and Smoky Mtns NW of Baldy, the persistent slab problem is much less likely to exist. However, on some upper elevation slopes, the wind slabs formed by recent snowfall and wind are sitting atop these same weak layers. Yesterday, a skier on in the Boulders intentionally triggered a small wind slab that was 18” thick. Look for evidence of wind drifting such as smooth pillows of snow, dune-like drifts, ripples on the snow surface, and fresh cornices along ridgelines. You’re more likely to find a wind slab sitting atop weak facets and/or crust sandwiches on upper elevation, NE-N-NW aspects.

Avalanche Discussion

Looking back at these last couple of months, I probably don’t have to remind you that February and the first half of March were all about clear skies and sunshine. This dry spell created weak, faceted snow surfaces, especially where the wind or sun could not get to the snow. Nowhere was this dry spell stronger than in the Pioneers and the mountains around the Wood River Valley, and it got to the point where, in many areas, the snowpack was completely rotten and faceted top to bottom. 

When snow finally returned, it did so favoring precisely this southeastern part of the forecasting area. Adding the biggest load to the weakest snow resulted in some big avalanches (link to Bens North Fk picture) around the North Fork of the Bigwood River and in the Pioneers. 

Further north, in the mountains around Galena Summit, weak surfaces—while still common—were less widespread. This area also received less snow when the taps turned back on. As a consequence, avalanche activity has been more spotty, with smaller, shallower slides. 

This pattern continues as we move north of the pass and into the Sawtooths. A less severe drought, less precipitation in the latest storms and little to no slab avalanches. As you might guess by now, the Banner Summit Zone too follows this pattern, and wind slabs on weak crust-facet combination—while not possible to rule out completely—are few and far between.

So what does this mean moving forward? It looks like we might have more moisture on tap in the coming week, and if this turns out to be true, we will start seeing more buried weak surfaces becoming “active”. The further north we go, the more snow and wind will be required for this to happen, and the problem is unlikely to be widespread.

Regions covered