Avalanche forecast

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Dangerous avalanche conditions exist—particularly on steep slopes with stiff deposits of wind drifted snow. The danger will remain elevated as the first of a series of storms impacts the area this afternoon. Avalanches can be triggered remotely—from below, above, and to the sides of steeper terrain.

Avalanche problems

  • Wind Slabs

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

    Beginning this afternoon, a series of storms are forecast to bring moderate wind and snow to the headwaters of the Salmon, Galena Summit and the White Clouds. Much less snow is expected in the Boulders and Pioneers. You may find small, touchy wind slabs as early as this evening, and likely by tomorrow morning. This problem will be most widespread at upper elevations with greater snow amounts that are exposed to stronger wind. 

    Be alert to this problem if you're out later in the day as fresh slabs can form in a surprisingly short amount of time. Look for active wind-loading and cracking in the snow surface. Small wind slab avalanches (see video to right/above) can be great triggers for more deeply buried weak layers. Any avalanche that steps down to these persistent weak layers will be large and destructive.

  • Persistent Slabs

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

    Two prominent persistent weak layers are worth tracking:

    1. Facets and isolated surface hoar buried 1-2' down: The late January and early February storms and recent multi-day wind event produced many natural and human-triggered avalanches on this layer. It was the likely culprit in countless avalanches in the past 2 weeks, including the large avalanches in the photo to the right/below. 
    2. December facets, now buried 3-4' down: The good news—this ugly layer has become harder to impact as the burial depth has increased. SAC forecasters and others are seeing fewer obvious signs of instability (like collapsing of the snowpack). The bad news—the first sign of instability you see may be a large, unsurvivable avalanche. This layer is trending towards a deep persistent slab problem: difficult to trigger but terrible consequences if you do.

    You are most likely to trigger a persistent slab in "prime time" avalanche terrain—slopes over about 35*—that has been loaded by the wind.  Keep in mind that these slides can be triggered remotely—from below, above, and to the sides of steeper terrain.

    (2/4/2021) These very large slab avalanches at the head of the Eagle Creek drainage likely released early in the morning on February 3rd. The largest slab in the foreground is over 1,000' wide. A very large avalanche is also visible in the background (West Fk Trail Creek). It appears to be at least 1,000' wide.

Avalanche Discussion

A series of storms are stacking up in the Pacific and snowfall will arrive in the majority of the forecast area by noon today. The first storm will bring snow this afternoon and into Friday morning. The second storm will bring an additional pulse of moisture during the day on Saturday. For both systems, expect a heavy bias toward greater snow amounts near Banner Summit, the Sawtooths, and the western Smoky Mountains. 

Portions of this zone near the headwaters of the Salmon and the northern Smokys to about Galena Summit may receive over a foot of snow by Sunday morning. During the storm, wind will generally blow moderate from the west. Expect the danger to rise tonight and tomorrow as accumulations stack up and wind redistributes this new snow into a fresh layer of sensitive wind slab. These slabs will be thicker and more widespread at upper elevations. 

This year, it's been difficult to disassociate new snow avalanche problems from the effect they have on buried weak layers. Today's fresh wind slabs and storm snow will add stress to the layers of surface hoar and facets described above. However, a general lack of recent avalanche activity, slowly improving snowpack test scores, and fewer reports of snowpack collapsing all suggest improvement. This zone will be tricky. The greater snow amounts will fall where the snowpack has shown the most improvement. While portions of the zone, with a shallower, weaker snowpack will receive less snow.

If that pattern continues, wind slabs may become the primary avalanche problem. Regardless, in the next few days finding safer places to play will primarily involve avoiding areas with recent wind-loading and obvious stiffer layers near the snow surface. 

Regions covered