Bollettino valanghe

Bollettino valanghe

Payette Avalanche Center
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Pericolo valanghe

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

In sintesi

Although becoming less likely, you could still trigger a persistent slab avalanche two feet thick. You're most likely to trigger a persistent slab avalanche on steep, wind-loaded slopes above 7000' that face NW, N, NE, or E. You can decrease your exposure by avoiding the terrain features described above. The weight of a snowmachine is more likely to impact buried weak layers than the weight of a person.

Problemi valanghivi

  • Persistent Slabs

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

    Over two feet of snow since last weekend sits on weak layers buried earlier this month. This persistent slab problem was responsible for a widespread avalanche cycle that occurred Sunday through Tuesday of this past week. Most of these avalanches were observed between 7-8000' on NW-E facing slopes. A lot of this activity occurred just below ridgelines on heavily wind-loaded slopes. Depending on aspect, there are crusts, facets, or surface hoar buried around 2 feet down. A few days of warm, dry weather have helped ease instability. This problem is becoming more difficult to trigger, especially from the weight of a person. The weight of a snowmachine will be able to cut deeper in the snowpack and is more likely to impact buried weak layers.

    Managing this problem is becoming tricky. The signs of instability are becoming less obvious over time. Natural avalanche activity has already spiked. As the likelihood of triggering begins to decrease, you can increase your margins of safety by avoiding problematic areas (i.e. steep, wind-loaded slopes that face NW, N, NE, and E). Ease into terrain that doesn't have big consequences and dig into the snow to look for buried weak layers.

Avalanche Discussion

Sunday, December 15th, a fatal avalanche accident occurred south of our forecast zone west of Cascade. You can read the preliminary report here. Our condolences go out to those impacted by this tragedy. The PAC will issue a full accident investigation in the coming weeks.

Last weekend kicked off an active start to the forecasting season. We saw a five to six day stretch of active weather with strong winds and over two feet of new snow (2-3" SWE). Natural and human-triggered avalanches were observed Sunday through Wednesday. Avalanche activity spiked sometime around Monday or Tuesday. The West Central mountains have been in a brief warm and dry period the latter half of this week. This dry period of weather has formed another round of weak snow at the surface. Surface hoar, crusts, and wind-stiffened surfaces have been observed in recent days. Weak snow and firm surfaces will be getting buried by new snow later today.  As tension slowly begins to ease on our existing Persistent Slab problem, we will be forming new avalanche problems later today and into Sunday. What are the differences between aspects and varying elevations? You can get a head start on these blossoming avalanche problems by paying close attention to what the snow surfaces are like before they get buried.

We've recieved some excellent observations over the past week. You can view those here. You can also submit an observation after a day in the mountains. Tell us what you saw or maybe what you expected to see and didn't. Some basic information and a photo or two can help improve avalanche forecasts.