Bollettino valanghe

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Mon
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 7 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

It remains possible to trigger an avalanche large enough to bury or injure a person, especially in upper-elevation, wind-loaded terrain. Watch for signs of instability such as snowpack collapsing and cracks shooting from your boards or sled. Choose conservative terrain with no evidence of wind drifting.

Problemi valanghivi

  • Persistent Slabs

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

    Several prominent persistent weak layers exist in our early-season snowpack (read Forecast Discussion below). Although this zone received less snowfall from Thursday's storm, it did get more wind. Also, yesterday's northwesterly winds blew more strongly than forecast—especially in the Soldiers. The resulting wind drifts may be a problem on their own, but the more serious issue is that they're adding additional weight to underlying weak layers. On Friday, riders in the Soldier Mountains triggered a small avalanche on a slope with signs of wind effect (see photo). 

    Choosing conservative terrain with no evidence of wind drifting is the best way to avoid triggering an avalanche. Be alert to signs of unstable snow such as cracking or collapsing—these are obvious indicators you've found dangerous conditions.

Avalanche Discussion

If you're a Cliff Notes type, here's the short story: our forecast area has a complex, early-season snowpack with several prominent weak layers. Thursday's storm produced varying amounts of snow and wind across our area, but natural or triggered avalanches occurred in each of our zones. The most recent of these occurred yesterday, with human-triggered avalanches in the Galena Summit area and in the Salmon Headwaters. Given the likelihood of triggering an avalanche—especially in our northern and western mountains—sticking to lower-angled terrain remains the best approach. Given the possibility of remote-triggering, recognize that you could trigger avalanches from above, to the side, or from below steeper slopes.

If you're ready for the longer story, let's take a closer look at some of the weak layers we're dealing with:

December 7th Surface Hoar:The December 7th storm buried a layer of surface hoar, which can be now found about 12-16 inches deep on many slopes. This layer has been responsible for most of the human-triggered avalanche activity since Thursday's storm, the most recent of which occurred yesterday. Friday on Banner Summit, Ben and I saw every sign of instability in the book: poor snowpack test scores, collapsing and cracking of the snowpack, and natural and remotely-triggered avalanches.

Thanksgiving Storm Snow:Thanksgiving brought some much-needed snowfall, but cold, clear weather following the storm quickly turned this to weak facets. This layer is most prominent in our southerly zones that received the brunt of the Thanksgiving storm, and is less common in our northern mountains that were left out of the Thanksgiving fun. This layer produced some remotely-triggered avalanches in the Eagle Creek drainage following the December 7th storm.

September and October Depth Hoar:The snow that fell in the early fall turned to well-developed facets and depth hoar during our dry November. This layer is most prominent on upper elevation, northerly-facing slopes and in alpine terrain - places where this snow didn't melt during the November drought. This layer is easily-identified—it's the large-grained, sugary snow found near the base of the snowpack. 

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