Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

A well-documented persistent weak layer continues to rear its head in the West South zone and maintain the avalanche danger. This poses a higher than normal sense of uncertainty about the snowpack. So, consider choosing simpler terrain where you can easily avoid large steep open slopes.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1.5–2.5

    This problem just doesn’t want to go away. A layer of buried surface hoar and preserved large stellars continue to linger 1-1.5ft (30-45cm) below the surface. While we haven’t heard of any new avalanches on this layer, it continues to fail suddenly in snowpack tests and demonstrates the ability to produce avalanches. So, while triggering this layer maybe unlikely, if you find the right spot, you could release a large avalanche that breaks above you. Unfortunately, it’s nearly impossible to tell exactly where his beast may still live. Then, how do we manage this uncertain problem? Seek out smaller and lower consequence terrain, and consider avoiding all large steep open slopes. This isn’t an isolated problem. NWAC forecasters and avalanche professionals observed this layer repeatably over the past week throughout the zone, on all aspects, and at all elevations.

Avalanche Discussion

While another Moderate danger day may feel routine, this snowpack is anything but. We know a  buried weak layer exists, but a lack of recent avalanches only increases our uncertainty. There’s an old adage, “when uncertainty goes up, terrain goes down.” That may be the best way to deal with this more unusual situation. 

Observations from Crystal Mt, White Pass, Mt Rainier, and Mt Adams this week all confirm the presence of buried surface hoar. A similar snowpack structure also exists in the nearby Mt Hood zone. On Thursday, an NWAC forecaster there found failures continuing to propagate across large column snowpack tests. So, while we feel like this layer is gaining strength, there’s enough data still pointing towards potential avalanches that we can’t let it drop from our minds. 

Friday will be yet another warm sunny day. This recent weather formed a thin sun crust on steep sunny slopes. This should soften during the day and you may see a few new rollerballs. Even still, it’s near the shortest day of the year. Any wet surface snow shouldn’t pose much real hazard. Away from sun-affected areas, soft dry snow continues to provide excellent travel conditions. 

We have a storm on the horizon. Several days of cold clear weather formed a new crop of surface hoar and facets. These could get buried in the coming snow. Today’s surface can become tomorrow’s weak layer. If you’re out, take a photo and let us know what you see before these weak grains get hidden from view.

Regioni coperte