Bollettino valanghe

Bollettino valanghe

Payette Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Recent SW winds have formed wind slabs 1 foot thick above 7000' on NE-facing terrain. Triggering a persistent slab avalanche 2-3 feet deep is possible, especially where the wind has loaded slopes. Poor snowpack structure and recent avalanche activity should keep your senses heightened today. Rain could be falling on cold, dry snow this afternoon creating wet loose avalanche activity and rising avalanche danger.

Today's forecast is sponsored by Mile High Powersports

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–1.5

    Yesterday, W/SW winds were blowing and drifting snow all day. There is a moderate amount of snow available for transport and the wind was taking advantage. You can expect to find fresh wind slabs around one foot thick above 7000'. You're most likely to encounter wind slabs on easterly aspects, near ridgelines. Local terrain features can alter prevailing wind patterns. Wind loading can be expected across multiple aspects as you gain elevation. Look for clues like shooting cracks from your skis, sled, or board. Pay attention to the snowpack collapsing and sounds like whumpfing. If you find fresh wind slabs, find a different aspect or choose low angle slopes (less than 30 degrees).

  • Persistent Slabs

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

    Persistent weak layers formed during a dry spell in late December, were buried on New Year's Day, and are now 2-3 feet deep. Although it's becoming less likely, triggering a persistent slab avalanche 2-3 feet deep remains possible today. This problem is widespread across multiple aspects and elevations. With weather events earlier this week, triggering a persistent slab avalanche below 7000' is unlikely. You're most likely to trigger a persistent slab avalanche in steep, wind-loaded terrain above 7000'.

    This link to our observation page shows the breakdown of instability and recent avalanche activity during the past week. We've observed several large, natural avalanches within the past 7-10 days. Instability peaked earlier this week. As the name implies, persistent slab problems tend to persist for a while even after instability has peaked. All of these persistent slab avalanches failed above 7000' on N, NE, and E facing slopes.

    (1/26/2024)

    Looking across the crown line, estimated 400' across

    Photo: Kevin Studley

Avalanche Discussion

Uncertainty

Yesterday, we toured near Josephine Lake. We observed two recent natural avalanches. You can view my observation here. Both of these avalanches failed on persistent weak layers buried several feet from the surface. They both looked to have occurred sometime between Wednesday night and Thursday evening. These deeper weak layers are getting difficult to trigger for two reasons: (1) they are buried several feet down and (2) a slab of very dense snow is resting on top of them. This gives us a false sense of stability. If you dig a snowpit and perform instability tests, you likely won't receive alarming results on these persistent weak layers. However, if you find this poor structure of a dense slab overlying persistent weak layers, watch out. Poor structure overrules test results, particularly false stable results. Recent avalanche activity combined with poor structure should keep your avalanche senses heightened today.

Coupled with this persistent slab problem is uncertainty. There is uncertainty about the weather events this weekend and how it will impact the snowpack. There's uncertainty about timing and how much precipitation the mountains could receive. If more moisture arrives earlier than anticipated, expect Wet Loose Avalanches to increase throughout the day. Rain on snow can create instant instability, especially when falling on cold, dry snow. There's uncertainty about how this rain event is going to impact our persistent slab problem. It seems unlikely that there will be enough saturation to produce Wet Slab Avalanches. However, rain on snow will add weight and strength to an already dense slab resting atop persistent weak layers. This could potentially increase the likelihood of triggering large, destructive avalanches by the afternoon/evening. With all of this uncertainty and poor snowpack structure, a conservative travel plan will be necessary this weekend.

Get your name in the hat to win some gear in our FPAC monthly drawing when you submit an observation. Submitting an observation improves your skills, informs other users, and benefits avalanche forecasts. Simple photos highlighting conditions are very helpful.

Did you know there are several avalanche classes in the area? Check out our classes and events page to learn more.