Avalanche forecast

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Warm temperatures and direct sunshine are creating dangerous avalanche conditions. Natural and human-triggered wet snow avalanches will increase in size and likelihood as the day heats up. If you're finding a thick pile of wet, mushy snow at the surface, conditions have become dangerous and you should consider avoiding avalanche terrain and terrain exposed to hazard from above. Avalanches may impact roadways on the valley floor. Dry snow avalanches failing on weak layers buried 1-2 feet deep remain possible and can be triggered from a distance away from the slope that slides. 

Avalanche problems

  • Loose Wet

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

    Widespread wet snow problems will develop with today's heat and sunshine. The snowpack weakly froze last night and it won't take long for the crust at the surface to break down. You'll be most likely to encounter and trigger wet snow avalanches on steep slopes receiving direct sunshine. Wet snow avalanches will also be problematic on steep, shaded slopes at lower and middle elevations as the day heats up. These avalanches start out small and pick up speed and material as they travel downslope. In favorable terrain (long, steep, and rocky slopes) these avalanches will entrain large amounts of debris and will be large enough to bury you today. As meltwater penetrates deeper into the snowpack, wet slab avalanches will become possible. These types of slides behave unpredictably and can be very large and destructive.

    If you're finding a thick pile of wet, mushy snow at the snow surface it is a good time to think about heading for home. This will happen much more quickly today than it did yesterday. Cascades of roller balls (wet balls of snow traveling downslope) are a good indicator that the snow surface is becoming wet. Conditions will be increasingly dangerous throughout the day. If you are chasing cold, dry snow up high, make sure you have a safe exit route in mind for the end of your day. 

    Read the Forecast Discussion below for more information about today's changing conditions. 

    (4/6/2023) Widespread wet loose avalanches were observed in the Sawtooth Mountains on Thursday, April 6. There is still a lot of dry snow that will be coming down off the mountains in the coming days.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–2.5

    Layers of weak snow buried underneath 1-2' thick slabs can produce large avalanches. The most recent triggered avalanche on these weak layers occurred on Wednesday when riders remotely triggered an impressive slide from 50 yards away (photo at right/above). The slide broke over 1,000' wide and 2' deep (more details here). I triggered a similarly large slide on Sunday north of Banner Summit (video here). Tuesday, on Mushroom Ridge, SAC staff experienced multiple large collapses and received poor snowpack test scores on slopes with a crust + facet weak layer. Most of the avalanches that we've observed on these layers have failed on crust + facet combinations. Most of the avalanches that we've observed on these layers have failed on crust + facet combinations.

    Avalanches that fail on these weak layers will be large and destructive and will behave in surprising ways. Slides can be triggered from a distance away from steeper slopes. Several skiers or riders might traverse a slope before it avalanches—tracks on a slope are not an indication of stability. You can reduce your risk by staying off (and out from beneath) slopes steeper than about 35 degrees.

    ADDITIONAL DISCUSSION: Older weak layers lay buried underneath very dense, 3-5' thick slabs. Triggering a very large avalanche involving these weak layers has become unlikely, but unlikely and impossible are very different things. The most recent triggered avalanche involving these older weak layers happened last Friday, when riders triggered a very large slide from over 500' away (photo and details here). Smaller triggered avalanches, natural wet snow avalanches, failing cornices, and percolating meltwater can all be effective triggers for these beasts. Being caught in one of these slides would likely be unsurvivable. 

    (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 Frenchman's drainage near Smiley Creek. You can clearly see the two sets of persistent weak layers in our snowpack in this photo. 

Avalanche Discussion

SNOWPACK IN TRANSITION - DAY 2

The great meltdown of our snowpack continues. We made it to the second week of April with a winter-flavored snowpack, but that changed significantly starting yesterday. Valley bottom temperatures hit 50 F and mountain temperatures climbed into the low 40s F. Observers reported finding wet snow on shaded aspects as high as 8,000' and multiple natural wet snow avalanches were observed. Up high, temperatures cooled into the 20s F overnight, allowing the surface of the snowpack to freeze. In the mountains above the Wood River Valley, temperatures are hovering on either side of freezing this morning (32 F) and a much weaker freeze took place. There is a lot of snow clinging to steep terrain in the mountains and the valleys that will be shed today.

If you head out around sunrise you'll likely find at least a thin crust on the surface of the snowpack in most places. But don't be fooled into thinking that you're dealing with a locked-up spring snowpack. This crust will quickly break down as temperatures warm and direct sun heats up the snow surface. Underneath the crusts, you'll find a warm, moist snowpack in the throes of its annual transition. Once the crust breaks down, wet snow avalanches will quickly follow. These will initially be on the small end, but will increase in size and frequency as the day heats up. Avalanches can gouge deeply into the wet snow underneath, producing very destructive wet slides. Wet slab avalanches will become increasingly likely over the coming days. Predicting the exact onset of wet slab avalanche cycles is next to impossible, but the conditions are ripe for these types of slides. 

These warm temperatures will eventually help the persistent slab problem on its path to healing, but that hasn't happened yet. If you are playing at upper elevations and in some middle elevation terrain you'll encounter a snowpack that is squarely between a winter and spring snowpack. Here, you'll find a range of other problems in addition to the persistent slab problem described in problem 2 above. Small wind slabs formed during recent storms may remain reactive to your weight. Look for cracks shooting out from your skis or machine as an indication of an unstable slab. Very large cornices will be sagging and deforming with today's heat. Cornices are unpredictable, but you definitely don't want to be out walking and riding on them or to be hanging out below them on a day like today. Large cornices can break much further back than you'd expect and can be very effective triggers for large slab avalanches on the slopes below. Lastly, if you head up high today in search of cold, dry snow, remember that you'll have to come back down through the elevation bands to get out at the end of the day. Conditions will be much more dangerous by this time.

Be prepared to encounter a wet, ugly, unstable snowpack today. Step back from steep, consequential avalanche terrain if you are finding a thick pile of wet, mushy snow at the surface. And don't forget to pay attention to the terrain above you—wet snow avalanches will be happening naturally throughout the day. 

Regions covered