Avalanche forecast

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

You could trigger avalanches big enough to bury people on some sheltered and wind-affected slopes. You may be able to trigger avalanches remotely—from gentler terrain above, below, and to the sides of steep slopes. Watch for soggy, wet snow at lower elevations this afternoon. To reduce your risk, you can stick to lower-angled terrain and avoid areas where the snowpack is wet or mushy.  

Conditions are most dangerous in the western half of this zone—Dollarhide Summit and the Soldier Mtns. 

Avalanche problems

  • Persistent Slabs

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

    The calendar says April, but we're still dealing with a mid-winter-style Persistent Slab problem (watch this video). This problem is by far the most likely way to "find trouble" today. We have two distinct problems to consider:

    1. "Fresh" Slabs: Sunday, thin slab avalanches released naturally just north of Hailey. You could trigger 1-2 foot thick slides on some middle and upper elevation slopes. Avalanches are most likely on slopes approaching or over about 35 degrees where crust + facet combinations or small facets exist in the upper 2 feet of the snowpack. Watch for snowpack cracking or collapsing, clear signs the snowpack is unstable. 
    2. Thicker, Older Slabs: It would take some bad luck to trigger a massive 3-6 foot thick avalanche in this zone, but we can't rule it out. These hard slabs also rest on weak facets and crust + facet combinations. The most recent triggered avalanche involving this snow occurred Friday in the Frenchman Ck drainage near Smiley Creek when riders remotely triggered a slide that broke 4-5 feet deep and 800+ feet wide (photo at right/above). The riders were at least 500 feet away on the ridgeline above when they triggered the slide. Triggering an avalanche involving this deeper weak layer is less likely than the thinner "fresh slabs", but the consequences would be devastating. Don't expect to see signs of instability associated with these thick, dense slabs. 

    The multiple persistent slab problems are challenging to manage. You may or may not see obvious signs of instability on unstable slopes, depending on the depth of the weak layer. You may be able to trigger slides from long distances away. Slides could break wider than you expect. Tracks on a slope are not a great indicator of stability. Unfortunately, the best management strategy is avoidance; staying off of slopes steeper than about 35 degrees will reduce your risk, but it won't eliminate it. 

    ADDITIONAL DISCUSSION: Adding to the complexity is the potential for wet avalanches. While they won't be huge, they could trigger the Persistent Slabs discussed above or carry you where you don't want to go. Muted sunshine and afternoon heating could cause natural, surficial wet loose slides involving the recent snowfall, especially on SE-S-SW-W aspects when they are directly facing the sun. In lower elevation terrain where the snowpack is thin, wet loose avalanches could gouge to the ground. Watch for rollerballs and pinwheels, signs the surface snow is becoming moist and unstable. Steer clear of steep slopes where you find a wet, mushy snowpack. 

    (3/31/2023)

    Crown of a very large avalanche that was remotely triggered by riders from at least 500 feet away on the ridgeline above. It broke 4-5 feet deep and 800+feet wide. This slope faces W at 9,300' in the Frencman's drainage near Smiley Creek. You can clearly see the two sets of persistent weak layers in our snowpack in this photo. 

  • Wind Slabs

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

     You may encounter relatively thin, fresh wind slabs in exposed middle and upper elevation terrain. Slabs will be thicker and more widespread in the western part of this zone where winds were stronger. Any wind slabs that you encounter may be perched above weak facets and/or crusts, making avalanches easier to trigger and wider than you'd expect. 

    Look for wind slabs near ridgelines and on the sides of mid-slope terrain features like gullies and ribs. Surface textures like dunes, ripples, or pillows are clues that the wind has been at work. Cracks shooting out from your skis or machine are clear indicators that you've found an unstable slab. 

    Cornices are unusually large this year. Give these unpredictable beasts plenty of space by traveling far from the edge, staying where you can easily feel dirt or rocks below your skis or sled. Large, falling cornice chunks and/or relatively small wind slabs moving downhill could trigger the larger, more dangerous Persistent Slab avalanches discussed above.   

     

    (4/2/2023) This wind slab avalanche released naturally on April 1st in the Left Fork of Fall Ck in the Pioneer Mtns (NE 10800'). Note the wind dunes and ripples on the bed surface of the slide. Tristan Pettigrew photo.

Avalanche Discussion

The cold, sputtery weather in the past 48 hours is preventing our Persistent Slab problem from fading off into the sunset.   A quick recap of some important observations from the past couple of days:

  • SAC forecasters remotely triggered two avalanches (Banner Summit video, Titus Ridge observation).
  • A regular observer reported multiple, large, natural avalanches released around noon Sunday near Copper Mtn on E aspects near 8500'.
  • Several medium-sized slab and loose snow avalanches released naturally on Sunday in the Wood River Valley south of Ketchum. All the slides were in west-facing, wind-loaded avalanche paths that were baking in the afternoon sun.
  • A regular observer reported several impressive recent natural avalanches in the Pioneer Mtns (observation).
  • SAC forecasters and observers reported dozens of recent large natural avalanches, including impressive slides on Galena Peak and farther south in the Boulder Mtns (observation with photos). 

Are there patterns in the recent activity? Many recent avalanches appeared to involve "prime time" slope angles of 35-45 degrees. Recent avalanches failed on many aspects: sunny S-SW slopes, slopes on the "margins" with partial shade and sun (W-NW and SE-E), and shadier aspects (NW-N-NE). Most of the recent activity appeared to involve crust + facet combinations in the upper 2 feet of the snowpack, but some slides were over 4 feet thick. Many of the recent slides were in relatively sheltered terrain, and many were over 500' wide. 

What can we do with that information? On slopes steeper than about 35 degrees, there's a chance you'll trigger a slide big enough to bury you and an outside chance the slide will be big enough to damage or destroy a house. Consider what's above you if you're sticking to gentler slopes; you could trigger avalanches from flat or mellow terrain below steep avalanche starting zones.  

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