Lawinenlagebericht

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

Sun and warm temperatures will turn the snow surface to mush. Natural and human-triggered wet avalanches are likely at low elevations and on any very steep slope that faces the sun. On cooler slopes, triggering a large avalanche remains possible where the wind has stiffened the snow.

Lawinenprobleme

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    The threat of natural and human-triggered wet avalanches will rise throughout the day and linger well into the evening (photo). Yesterday, numerous wet avalanches were observed across the forecast area (observation, observation). Yesterday was the hottest day of the year, followed by the warmest night of the year. Today will be another scorcher. 

    Yesterday's heat pumped a lot of water into the snowpack. Last night's weak (shallow) or non-existent freeze means today's meltdown will get a "head start". Thin crusts will break down quickly on any slope that faces the sun. Most slopes, especially those at low elevations will turn to mush as temperatures climb to near 60 F.

    Rapid melting at the surface and meltwater moving through the snowpack can cause a variety of wet avalanche problems. You can read more about these scenarios in the Forecast Discussion below. Predicting wet avalanches can be difficult. Thankfully, avoiding the time of day and terrain where they're most likely is relatively simple.

    Avoid very steep slopes that face the sun, especially those above terrain traps. More slopes will become unstable as the day heats up. If you find yourself sinking into a mushy snowpack find cooler snow or stick to lower angle slopes. Plan to pack it in early and give yourself options, including a safer, low-angled exit that's not threatened from above.

    (3/23/2022) Wet loose avalanches on E and SE facing terrain in Mill and Prairie Ck drainages.

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Skiers and riders triggered several slab avalanches in the past week. All involved persistent weak layers (crusts + facets, or simply facets) in the upper 1-2 feet of the snowpack. Some were triggered remotely—from gentler terrain above, below, or to the side of the slab (photo, photo). 

    You are most likely to trigger a persistent slab avalanche on shadier, very steep slopes where the wind has built a stiffer, denser slab. While less likely, triggering slabs in sheltered terrain can't be entirely ruled out. You can significantly reduce the odds of triggering a large slab avalanche by sticking to slopes less than about 35 degrees that are typically sheltered from the wind. 

    (3/18/2022) Riders triggered this avalanche in the Baker Creek drainage of the Smoky Mtns. It occurred on a wind-loaded, NE-facing slope at 9500'. It broke over 100' wide and 10-16" thick.

Avalanche Discussion

WET AVALANCHE CONCERNS

It's Day 2 of an extended warmup. Here are a few wet avalanche scenarios you need to consider:

Thin Wet Loose Slides: These avalanches are commonly small. They are not likely to bury you but can sweep you off of your feet and carry you where you don't want to go. They often originate near warm cliff bands and rocks on very steep slopes that directly face the sun. They are most prevalent in the Smokys, White Clouds, Sawtooths, and near Banner Summit where there's more recent soft snow at the surface. Dozens of these slides were reported yesterday from all across the forecast area. While the "prime" locations for these avalanches have flushed, I'd expect to see more of these today. 

Gouging Wet Loose Slides: These large wet avalanches are more likely today. Yesterday's heat and mild overnight temperatures mean any crust you find this morning is likely to be thin. Hiding below the crust is a goopy mess of wet, unfrozen snow. The deeper this layer of wet snow gets, the larger the potential slide. Thin wet loose slides that originate at upper elevations can tap into deeper wet snow as they cascade down warm mid-elevation slopes. Where the snowpack is less than about 2 feet thick, some slides could involve the entire snowpack. These avalanches are most likely on very steep, rocky slopes that are sheltered from the wind.

Wet Slabs: These avalanches can be large and destructive. Wet slabs occur when meltwater pools and spreads along a weak layer in the snowpack, weakening the bond of the overlying slab. These slides are notoriously difficult to predict. Their occurrence depends on several variables that are unknowable on any given slope. However, we do have the main ingredients for a potential wet slab avalanche problem to arise; defined weak layers of snow and plenty of meltwater production. It's not uncommon to see loose avalanches "flank out" or widen to release a wet slab lower on a slope. Today is only Day 2 of a prolonged warmup. This problem will remain an uncertain undercurrent as long as the snowpack remains mostly wet. 

It's important to address the uncertainty associated with forecasting wet snow avalanches but rather than getting lost in the weeds let's take stock of what we know. We have several factors going against us: record warm temperatures, long hours of hot spring sun (high sun angle), consecutive weak freezes, progressively more water in the snowpack, persistent weak layers and crusts that can pool meltwater, and lots of faceted snow that can quickly turn to mush. All of these factors get worse in the next few days but it's hard to know when/if the mountains will come completely unglued. Unfortunately, the only way to manage uncertainty is avoidance. Stepping back from very steep, consequential terrain is the prudent play wherever water is moving down into the snowpack. Let the heatwave run its course, watch the show, and postpone those big adventurous days in the mountains until we get through this transitional period. 

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