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

The avalanche danger will rise to CONSIDERABLE as the day warms and the snow becomes wet. Wet snow avalanches will be easy to trigger and will release naturally in steep, rocky terrain receiving direct sun. These slides can become large and destructive. Both dry and wet slab avalanches failing on layers of weak snow in the upper few feet of the snowpack are possible. Avalanches that break down into these weak layers will be unsurvivable if they catch you. These slides will break widely and are unlikely to be preceded by obvious signs of instability. 

Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2.5

    Mountain temperatures start on either side of freezing this morning (see 3-day temperature graph at right/above). Today will be 3-5 degrees F warmer than yesterday. Widespread crusts at the snow surface will break down quickly as the sun returns and temperatures spike. Wet snow avalanches involving the most recent snow will become easy to trigger and will release naturally throughout the day. These wet snow avalanches will come in two flavors today:

    LOOSE: These slides start at a point and gather speed and debris as they travel downslope. These will be easy to trigger and will release naturally today, often starting in rocky terrain or near trees that are pushing additional heat into the snow. Many of these slides will be small, but they can become large and destructive in steep, open terrain and in gullies and couloirs that channel the flowing debris. In areas where the snowpack is less than a few feet thick, avalanches may gouge through and entrain the thin, saturated snowpack and run near the ground. 

    SLABS: As the snow surface melts, the water is pushed deeper into the snowpack. As this water saturates the snowpack and pools at crusts and weak layers, wet slab avalanches appear on the menu. These slides are unpredictable and will produce very destructive avalanches. The good folks at Sun Valley Heli Ski observed a few recent large slab avalanches yesterday that appeared to have a wet character to them (photo here). The likelihood of these types of slides is increasing as the multi-day warming trend continues.

    Wet snow problems will be at their worst during the heat of the day on slopes receiving direct sunshine. Shaded low elevation slopes will become warm enough today that you may be able to push small wet snow avalanches in steep terrain. Pay attention to the snow you are traveling through and the terrain you are exposed to from above. Today is not a good day to linger on or below sunny slopes that can produce avalanches. 

    3-day temperature graph for Galena Summit SNOTEL (8,780').

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Widespread layers of weak snow can produce large avalanches here. These are buried beneath dense, 1-4 plus foot thick slabs, which makes triggering slides more difficult. These thick slabs also mean that any slide you trigger will be large and destructive. Do not expect feedback to receive obvious feedback from the snowpack today. The first sign of instability may be the large, wide avalanche that you trigger. These slides can be triggered after dozens of skiers or riders have traversed a slope. Triggered slides are likely to break far above you, making escape difficult to impossible. 

    Avalanche activity during major storms in March was widespread, occurring on all aspects. Many huge slides in this zone failed on persistent weak layers in the upper and middle portion of the snowpack. You'll find a variety of weak layers here (crusts with facets on solar slopes, and facets without crusts on shaded slopes). As meltwater percolates through the snowpack it can weaken the bonds underneath dense slab, producing large wet slab avalanches. Similar conditions at the end of January produced a widespread cycle of wet slab avalanche activity. Most of the slides observed then were large enough to destroy your house. 

    Triggering a slide is most likely in steep, rocky, open, heavily wind-affected terrain (photo at right/above). You can reduce your risk by avoiding this type of terrain. 

    (3/6/2024) Very large avalanche on a SE aspect above Window Lake north of Boulder Basin. Photo: Sun Valley Heli Ski

Avalanche Discussion

Wet Snow Behaves in Mysterious Ways

We are moving into the 4th day of an extended period of high pressure, warm temperatures, and weak overnight freezes. This is the first major warm-up of the season, and the snowpack is going through some major transitions during this time. The weather is screaming, "SPRING!", but the snowpack lags behind. As the warm-up progresses, the wet snow problems we are experiencing in the snowpack become larger, more dangerous, and more unpredictable. 

An icy crust formed at the snow surface overnight. Mountain temperatures are hovering on either side of freezing (32 F) and the snowpack starts the day warm. Air temperatures heat up fast, bringing on wet snow problems as the crust melts. Sustained S-SW winds over the past weeks formed massive, unstable cornices and packed snow into all sorts of unusual places. The mountains will continue to shed this snow today. Failing cornices and smaller wet loose avalanches can produce large avalanches as they travel downslope. Dry and wet snow avalanches that break down into deeper weak layers in the snowpack will be unsurvivable if they catch you.

When wet snow issues come to the table, we find ourselves searching for dry snow on cold slopes. Unfortunately, we can't avoid all of our avalanche problems simply by avoiding the wet snow. Layers of weak snow are buried across our forecast area. In the northern and western mountains, these layers are more deeply buried and the likelihood of triggering slides on them have gradually decreased. However, the large, frightening slide that was triggered in a steep couloir in the Sawtooths on Thursday clearly points to the potential for these layers to make deadly avalanches (photos here and here). The slide broke 2-4+ feet deep as the party climbed the couloir. It blasted down the slope at high speed, coming to a rest over 1,200' below. In our southern and eastern mountains, these weak layers are closer to the surface and they may be a bit easier to impact with your weight. Meltwater produced at the surface is likely to reach these layers today and in the coming days, weakening the bonds are creating the potential for destructive wet slab avalanches. The good folks at Sun Valley Heli Ski observed a few recent large slab avalanches yesterday that appeared to have a wet character to them (photo here).

As the day progresses, it will be harder and harder to avoid wet snow issues. Even steep, north-facing couloirs have walls that face west and east that may be receiving sun. Pay close attention to the terrain above you as well as the terrain you are moving through. And expect avalanche danger and the likelihood of triggering avalanches to change quickly. 

Today is another great day to start early and be out of the way early. Avalanche conditions will be more dangerous when you are exiting the mountains than they were on your ride in. The slopes that you comfortably traveled on and under will be more hazardous on your way home. Don't let the sun lull you into a sense of complacency, traveling through the mountains and returning home safely demands your attention today. Don't linger in runout zones below large starting zones that are receiving direct sunshine. 

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