Lawinenlagebericht

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Sat
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

Wednesday, skiers triggered a large avalanche where the wind formed drifts and stiffened the snow surface. Similar triggered avalanches are possible today. The fresh slabs are thickest and most widespread in upper elevation terrain. Expect numerous small loose snow avalanches on slopes that face the sun. While not likely, large avalanches failing on weak snow deeper in the snowpack are possible in wind-swept, rocky, alpine terrain.

Lawinenprobleme

  • Wind Slabs

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

    Recent snowfall and shifting wind has formed fresh wind slabs in exposed terrain. Wednesday, snowmobilers triggered small wind slab avalanches in the southern Sawtooths. One rider was caught and carried but was unharmed (report). In the Smoky Mountains near Titus Peak, skiers remote triggered a large avalanche from a low angle ridgeline (photo above/right, report). Over the past week, multiple large natural avalanches released in wind-loaded upper elevation terrain of the Sawtooths and Smokys (list). 

    Wind slabs formed atop a variety of weak snow layers, including facets on shadier slopes and facets or crusts on sunnier W-SW-S-SE aspects. Smaller wind slabs on sunnier slopes have shown the potential to step down to deeper buried weak layers resulting in very large, destructive slides (report). Light to moderate wind and ongoing light snowfall has made some wind-loaded slopes hard to identify. Look carefully for drifts and pillows of snow below exposed ridgelines, on the sides of gullies or chutes, and near large terrain features. While more prevalent at upper elevations, some slabs may exist on windier middle elevation slopes. Snowpack collapsing or cracks shooting out from your skis or sled are obvious signs of instability. 

    (2/22/2023) This avalanche was triggered near Titus Pk by a group of skiers on a low-angle ridge line. It released below them on a wind-loaded E and SE facing slope at about 9,800'.

  • Persistent Slabs

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

    Triggering a large persistent slab avalanche on weak, sugary facets buried deeper in the snowpack would take some bad luck. The video to the right/above describes this problem. Where are you most likely to find this scenario? On slopes with all or most of the following characteristics:

    • Wind-swept alpine terrain, especially in the Pioneer, Boulder, and White Cloud Mountains.
    • Steeper than about 35 degrees.
    • Variable snowpack depths with areas less than 2 feet deep and/or rocks poking through the snow surface.
    • Large, hard wind features somewhere on the slope.

    Don't expect to see or hear obvious signs of instability (snowpack collapsing or cracking) before a large avalanche releases. Snowpack stability tests are of little use in situations like this. The best way to manage this problem is to avoid terrain that checks all or most of the "boxes" above. 

Avalanche Discussion

Steering clear of recently formed drifts and slabs is the most effective way to stay out of trouble. Yesterday, observers reported snowpack cracking and collapsing in fresh wind deposits near Galena Summit. While wind speeds across the region were generally light, they were strong enough to move yesterday's snowfall into a fresh batch of thin, sensitive slabs. Some of these slabs extend into middle elevation. Wind-drifted snow may not be obvious as signs of recent wind affect are cloaked by shifting wind directions and low-density snow. Today's weather looks fairly benign, but I'd be prepared with a "Plan B" in case you encounter more wind or thicker recent drifts than anticipated. 

While fairly minor, there is one other scenario to keep in mind as you prepare to head into the mountains:

  • Loose Snow Avalanches: Around a foot of snow has fallen in this zone since Sunday. This recent low-density snow sits atop extremely weak facets on some NW-N-NE-E facing slopes. On very steep slopes approaching 40 degrees, it won't take much to get surficial sluffs moving (photo). Today will be mostly clear. Direct sunshine will trigger numerous natural loose snow avalanches. These probably won't be big enough to bury you, but they can pack a punch and could knock you over, pushing you where you don't want to go. Sluffs have the potential to trigger wind slab avalanches when recent winds formed stiff drifts lower in cirques and on the aprons of chutes and couloirs. 

Pay attention to the terrain above you. Remember that even small avalanches can have bad outcomes in complex terrain. Before committing to skiing or riding a slope, think about where an avalanche could carry you. Could you get pushed over cliffs, through trees, or into creeks or gullies? Slopes with these terrain traps are inherently more dangerous than open slopes with a clean runout.

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