Bollettino valanghe

West Slopes North

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Sun
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
Open full map
Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Very dangerous avalanche conditions exist as a warmer storm dumps snow Friday night through Saturday. Avoid steep terrain while the storm runs its course. Steer around the runouts beneath large, steep avalanche paths, even if the area you’re in is flat.

Problemi valanghivi

  • Storm Slabs

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

    We're getting a lot of water, warming temperatures, and plenty of wind during this storm. Just one of those factors may be enough to cause a spike in avalanche danger, but all three combined definitely makes the alarm bells go off. This is a great recipe for avalanches.  

    You can easily trigger an avalanche on steep slopes in the fresh storm snow. Temperatures will increase during the storm on Saturday, leading to “upside down” snowpack characteristics. This means that snow at the surface will be thicker and heavier than the snow beneath it. The heavier snow forms a slab that could easily slide on the lighter snow beneath it. Strong winds will also redistribute snow at upper elevations into thicker and more reactive slabs.

    Feel for a "punchy" snowpack as you step, where heavier snow overlies lighter snow. Watch for obvious clues such as cracking, collapsing, and recent avalanches. The incoming snow may tip the scale on avalanches very quickly, before you even have a chance to register the change.  All these factors taken into account, give avalanche terrain a wide berth on Saturday. You can still get out and play in lower angle terrain away from large overhead avalanche paths. 

     

     

    Touchy storm slab conditions like this example from last year are expected on Saturday. Photo: Irene Henninger

  • Loose Wet

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

    Warmer temperatures at lower elevations could lead to wet snow conditions. Rollerballs and small loose wet avalanches are likely to occur in the wet snow surface. When you start noticing small rollerballs running down a slope, this may be a precursor to wet loose avalanches. Stay off steep slopes when you notice rollerballs frequently rolling down a slope and picking up more snow as they roll. 

    Rollerballs are a great indicator that wet loose avalanches could start coming down soon. Photo: Andrew Kiefer

Avalanche Discussion

Several observers on Friday reported that the preexisting snow surface had weak snow crystals, in some places both surface hoar and facets. This means that the new snow layer could have an even easier time sliding on the old snow surface.  There is a lot of uncertainty with several of the factors of this approaching storm. Tread carefully in the backcountry during this storm. Continue to stay alert for early season hazards such as creeks, trees and rocks in lower elevation areas. They may become more pronounced as lower elevations will probably have a net loss of snow cover in the next 24 hours. 

Regioni coperte