Bollettino valanghe

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Sat
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
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In sintesi

Heavy snowfall and wind-drifting are creating very dangerous avalanche conditions. Natural and human-triggered avalanches are almost certain. Stay off of and out from below all steep slopes. Avalanches can be triggered remotely—from below, above, and to the sides of steeper terrain.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Certain
    Dimensione
    1–2

    This zone has received 1.5-3' of snow (1.1-2.2" SWE) since Tuesday night favoring the southern Sawtooths near Smiley Creek and western Smoky Mountains. Air temperature has continued to warm slightly as the snow piles up which aids in the formation of top-heavy slabs of snow on many aspects. These slabs are forming on a variety of weak snow surfaces including facets, crusts and facets, surface hoar, and wind-hammered ice. Observers in the Soldiers, the Wood River Valley, and the Sawtooths (photo) have found very sensitive slabs of new snow, failing on a layer of facets above a crust.  

    Moderate to strong SE wind has moved a substantial amount of snow at all elevations. Expect slabs to be thicker, stiffer, and more dangerous in windier terrain. Areas of wind-drifted snow may be hard to identify due to low visibility and continuing snowfall. This problem will become more dangerous as snow and wind continue throughout the day. These slides have the potential to "step-down" causing avalanches to fail on more deeply buried weak layers near the ground (see Persistent Slab problem).

    (1/27/2021) Cracking in freshly formed drifts along the Fishhook drainage in the Sawtooth Mountains. This photo is from early in the storm, conditions have considerably worsened since.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    Today's snowfall and wind-drifting are stressing weak, faceted snow buried over 3' deep. This weak layer has been the culprit in almost all of the avalanches we've observed this season. Avalanches are most likely where the snowpack is thinner, such as steep, rocky, upper elevation terrain that is affected by the wind. An overall thinner snowpack also exists in the mountains near the mouths of the major drainages near Smiley Creek. This avalanche occurred yesterday above Titus Lake near Galena Summit. It was likely triggered remotely from the low angle ridgeline above. 

    As snow piles up, smaller avalanches failing near the snow surface are likely. These slides can trigger larger persistent slab avalanches as they move downhill. Very large avalanches may run into valley bottoms—avoid all avalanche terrain. Remotely-triggering slides, from flat terrain below steep slopes, is a real possibility. 

    (1/28/2021) Avalanche above Titus Lake that was likely remotely-triggered from the ridge above.

Avalanche Discussion

AVALANCHE WARNINGS are in effect for the Sawtooth & Western Smoky, Galena Summit & Eastern Mountains, and Soldier & Wood River Valley Zones. Heavy snowfall has favored the southern and western portions of this zone toward Atlanta and Smiley Creek. 

Very dangerous avalanche conditions exist. Large, destructive, natural, and human-triggered avalanches are near certain. There are a host of scenarios that could send large avalanches hurtling down steep slopes today. Our snowpack has touchy weak layers under the recent storm snow, as well as a remarkably weak foundation of faceted snow. Expect avalanches to occur on many slopes, potentially breaking in unusual locations and wider than expected. 

Yesterday's observations were limited by difficult travel and poor visibility. Despite that fact, we didn't need to look for avalanches as much as we just needed to stay out of the way. Here are some notable events from yesterday:

Snowfall will diminish today, but avalanche conditions will remain very dangerous. Avoid all avalanche terrain. This includes flat slopes in the valley bottom that are threatened from above.

Regioni coperte