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
3 · Marcato
Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Triggering a 2-3 foot thick persistent slab avalanche remains possible, especially in/around the West Mountain zone. With 45-75 cm (18-30") of very light snow in recent days, dry loose avalanches (or sluffs) are likely on slopes steeper than 35 degrees.  

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    Persistent weak layers of buried surface hoar and facets have been overloaded in recent days. These buried weak layers lay anywhere from 2-3 feet beneath the snow surface. Our advisory area has seen 45-75 cm (18-30") of snowfall since Friday (03/03). Although recent snowfall has been very light, you are most likely to encounter a persistent slab avalanche in wind-exposed terrain above 7000. A snowmobiler triggered a large avalanche north of Snowbank Mtn, just west of the town of Cascade on Sunday (view observation here). Persistent slab conditions have been more reactive in the southern end of our zone (West Mountain). In areas north and east of McCall, you are most likely to encounter a persistent slab on aspects that are tilted toward the sun. Facets have formed above melt-freeze crusts buried 3 feet beneath the surface.

    Persistent slab problems are difficult to manage and can behave in unpredictable ways. Digging into the snowpack is the only way to tell if buried weak layers are lurking. Even then, buried weak layers (especially buried surface hoar) can be spotty and difficult to find. Never base a "go or no-go decision" on one snow pit. The only sure way to avoid a persistent slab avalanche is to minimize exposure on, around, and underneath slopes steeper than 30 degrees.

    (3/5/2023)

    The public submitted this observation of a large snowmobile-triggered avalanche. SS-AMu-R3-D3-E-7500'. 

    Photo: Public

  • Loose Dry

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

    45-75 cm (18-30") of low-density snowfall since Friday (03/03) has been very soft and mostly unconsolidated. In wind-protected areas, this recent snow has not yet shown the ability to form a slab. Dry loose avalanches (or sluff) can be easily triggered by the weight of a person or snowmachine. With over 2 feet of soft snow, these avalanches could be large enough to bury a person. You are likely to encounter dry loose avalanches on all aspects. The likelihood will be greatest on slopes steeper than 35 degrees that face north.

    Dry loose avalanches are often seen as manageable. Six inches of snow is much easier to manage than 2 feet of snow. If you find yourself in terrain where dry loose snow is moving, practice safe travel protocols and avoid terrain traps (gullies, depressions, cliffs). 

Avalanche Discussion

Today's avalanche forecast is sponsored by Franklin Building Supply of McCall. Thanks for supporting the Payette Avalanche Center.

With over 2 feet of low-density snow (less than 10%) in recent days, the storm snow is soft and unconsolidated. Winds have been light and wind slab formation has been isolated. It doesn't take much to move this light snow around and form stiff slabs. In terrain above 7000 feet, there may be pockets of wind slabs. If the winds increase today, be prepared to encounter wind slabs on leeward slopes/gullies and below ridgelines. 

The PAC received a photo thirdhand of an avalanche on the west face of Slab Butte. Information about this avalanche is limited. If you have more information, please submit an observation here.