Lawinenlagebericht

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 4 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

To reduce the chance of triggering avalanches, avoid slopes where the wind recently formed drifts or slabs. In areas more protected from the wind, triggering a 1-2 foot thick avalanche is less likely but not out of the question. Pay attention to the consequences of being caught in even small slides in terrain with rocks, cliffs, trees, and terrain traps.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2.5

    What is it?  Multiple weak layers exist in the snowpack. Some are just being buried by recent storms in the last couple of weeks. The most prominent of these is buried surface hoar down 1-1.5 feet on many sheltered, shady (W-N-E) slopes. This layer produced a number of triggered slides during the second half of January. Older weak layers (crusts and/or facets, occasionally surface hoar) exist deeper in the snowpack. 

    Where is it? You're most likely to find trouble on slopes steeper than about 35 degrees where the wind has formed drifts or slabs or stiffened the snow surface. The surface hoar is most widespread and problematic in somewhat protected, middle-elevation terrain that faces W-N-E. Older weak layers (crusts and/or facets, occasionally surface hoar) can be found in rocky, wind-affected, alpine terrain where the snowpack is less than about 3 feet thick. Watch Ethan's video (right/above) to get a picture of the terrain where these layers are most likely to be problematic.

    How can you recognize it?  Wind-loaded slopes have harder surfaces and a distinct appearance (video to right/above). You may or may not experience snowpack collapsing and/or cracking while traveling. These red flags are obvious signs of instability. 

    How can you manage it?  You can reduce your risk by avoiding very steep (greater than about 35 degrees), shady slopes (facing W-N-E) with hard or stiff wind-blown snow at the surface—especially those with ugly consequences if you are caught in an avalanche. Persistent slab avalanches may break wider than expected or higher on the slope above you. 

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–1.5

    What is it? Expect to find some stiff or hard wind slabs in exposed terrain. Sunday's new snow and wind produced some natural avalanche activity, and yesterday's moderate winds continued to build fresh slabs. Though not huge, these wind slabs could be sensitive to your weight and are stressing the buried weak layers described in Problem 1 above. 

    Where is it?  You may find wind slabs near ridgelines, on the sides of gullies and chutes, near prominent mid-slope terrain features, and on aprons below chutes and couloirs. 

    How can you recognize it?  Cracks shooting out from your skis or sled are an obvious sign of instability. Watch for drifts, dunes, and ripples on the snow surface. Wind slabs can have a smooth, chalky appearance and feel and sound hollow, like a drum. Wind-deposited snow will be stiffer and keep your skis or snowmobile on or closer to the surface.       

    How can you manage it?  The easy move is to avoid obviously wind-loaded slopes steeper than about 35 degrees. Hard slab avalanches can behave unpredictably, breaking above skiers and riders. Small triggered wind slabs have the potential to "step-down" to buried persistent weak layers (Problem 1) lower on slopes, causing a larger destructive avalanche.  

    (1/29/2023) This recent small wind slab released naturally on Titus Ridge near Galena Summit. It failed on a E/NE-facing slope at 9,600'.

Avalanche Discussion

Wind-affected snow remains the most dangerous piece of the puzzle to triggering an avalanche. Slopes that house several weak layers can be stressed by this added weight on top of the existing slab. Recent storms are slowly building a slab over weak layers in the upper snowpack. We have yet to see a lot of avalanche activity on this layer, but snowpit test results continue to indicate poor results. The most recent avalanche occurred on buried surface hoar released near Titus Ridge on January 29th (report). This layer is showing signs of improvement. However, surface hoar is an unpredictable weak layer; most of us aren't ready to write it off just yet. In the Galena Summit & Eastern Mtns, and Soldiers Mtns, older weak snow exists where the snowpack is less than 3 feet thick. You are more likely to find this issue in the alpine, where slopes steeper than about 35 degrees have rocky, wind-affected thin trigger spots can be found. 

Moderate to strong northerly winds have transported new snow creating hard and soft slabs of the Forecast area. Most avalanches have been small, but where they overlay persistent slabs is the most concerning.  In the mountains surrounding the Wood River Valley, wind slabs are more dangerous than persistent slabs. 

A stockpile of cold days created an upper snowpack mainly composed of faceted snow (most prominent in the Wood River Valley). This weak snow doesn't like to bond well with other snow. Playing in terrain steeper than about 35 degrees can produce "facet-lanches" in this type of snowpack. These avalanches start at a point and entrain more weak snow as they descend the slope (see field report). They aren't usually big enough to bury you. However, they become dangerous when riders get knocked over and carried through trees, cliffs, gulleys, or other terrain traps. This loose snow problem can also occur when the intense, strong sun comes out today. Sunny, rocky slopes steeper than about 35 degrees can produce wet loose slides as the sun rotates around the compass and melts the snow. 

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