Bollettino valanghe

Bollettino valanghe

Payette Avalanche Center
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Pericolo valanghe

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

In sintesi

Triggering a wind slab avalanche one or more feet thick will become likely today. Wind slabs will be thickest and most dangerous above 7000', on steep north and east-facing terrain, especially near ridgelines. Triggering a deeper, persistent slab avalanche is possible on weak layers buried last week. Dial back your terrain choices today by avoiding steep, wind-loaded slopes.

Problemi valanghivi

  • Wind Slabs

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

    Wind slabs one or more feet thick will become sensitive to human triggering today. Winds have been steadily blowing out of the W/SW over the past several days at upper elevations. Recent snowfall this week has created a moderate amount of snow available for transport. Yesterday, we observed recent (and current) wind transport onto east aspects. Winds are forecasted to continue all weekend with more snowfall, increasing the likelihood and the size of triggering a wind slab. Wind slabs will be most dangerous above 7000', on north and east-facing slopes, especially near ridgelines.

    Local terrain features can influence prevailing winds and may cause loading on other aspects at upper elevations. Pay attention to clues like shooting cracks from your skis, sled, or board. Look for dunes, drifts, or pillows that indicate recent wind loading. Avoid steep slopes that have been recently (or are currently) wind-loaded.

    (12/27/2024)

    Drifts on the leeward side of the trees. Indicating SW winds (right side of picture).

    Photo: Kevin Studley

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2

    Snowfall over the past week has buried crusts and facets (weak, sugar snow). Most were buried around the Winter Solstice (12/20-21) and have seen 1-2 feet of new snow since then. Professionals up Lick Creek reported reactive test results and evidence of natural avalanches on these buried weak layers earlier this week. Reactivity of this persistent slab problem has been fairly quiet the latter half of this week. We've seen incremental loading all week and this weekend we're looking at an additional 1-2 feet of snow. A dense slab of more than 2 feet of snow will be adding stress to these layers over the weekend. Uncertainty remains slighter higher for this avalanche problem and should be treated with a healthy dose of caution. You may not see obvious red flags (like cracking or whumpfing) with this problem. The best way to manage this problem is to give the snowpack time to adjust to recent stress by staying off slopes steeper than 30 degrees. 

Avalanche Discussion

The latter half of December has been active for snow and avalanches. The West Central Mountains have received accumulating snowfall in 13 out of the past 16 days. Mother Nature got the memo and it's been snowing everyday since the first day of winter. We've received moderate to light amounts of snowfall this past week and this weekend we are forecasted to see another 1-2 feet. Small, consistent storms have allowed incremental loading to the snowpack (i.e. little bit here, a little bit there, a little bit more). This process of incremental loading has not pushed our current snowpack to a tipping point. This weekend's storms may do just that. Adding an additional 1-2 feet with gusty SW winds could push our current snowpack over the edge. Avalanche conditions will become most dangerous this afternoon into the overnight hours. 

Safe travel protocols will be especially important as avalanche conditions become dangerous. Well, what are they you might ask? 

  • Traveling one at a time on slopes steeper than 30 degrees.
  • Selecting safe spots to stop with your group away from avalanche runouts.
  • Having a good travel plan with your group about which terrain you want to travel in and which terrain you want to avoid (and sticking with your plan).
  • Avoiding terrain traps that can make the consequences of an avalanche much worse (gullies, depressions, flat transitions, steep terrain above cliffs or trees, etc.)  

We've received some great observations this month and we can always use more. You can view those here. You can submit an observation after a day in the mountains. Tell us what you saw or what you expected to see and didn't. Some basic information and a photo or two can help improve avalanche forecasts.