Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Nice weather will help you spot and manage avalanche issues Saturday. You’ll need to navigate natural wet slides from steep southerly slopes and lingering slabs in rocky wind-loaded terrain. Be particularly leery of areas where even small slides could push you into a creek, over a cliff, or down a chute.

Problemi valanghivi

  • Loose Wet

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

    With Saturday’s warm sunny weather, we’re pretty confident you’ll see at least a few loose wet avalanches. Fortunately, you should easily be able to anticipate when this problem is rearing its head. Look for snow shedding from trees/rocks and new rollerballs indicate the scales are tipping. When you see these clues, start paying attention to the terrain above you. Natural wet slides will likely follow on similar sunny slopes. 

    Obviously, you can simply avoid this problem by seeking out shadier aspects. If you do choose to travel in sunny avalanche terrain, only expose one member of your team at a time and consider the consequences of any terrain traps below. On bigger slopes, some of these slides could entrain enough snow to grow large and more dangerous.

    (2/10/2023)

    Natural loose wet avalanches on Hogback Mt in the White Pass backcountry Firday. SE, 6500ft, LW-N-D1.5-R1-S

    Photo: Nate Hough-Snee

  • Wind Slabs

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

    We’re using this problem to communicate lingering slab issues from this week’s storms. We think you’re most likely to run into one of these slides in very steep, unsupported, and wind-loaded terrain. A slab avalanche could fail on any number of inter-storm layers above the 2/3 interface. In a few isolated locations, observations from this week found weak snow (facets and surface hoar) at this spot in the snowpack. 

    Take this into consideration before you commit to bigger and more complex terrain. Look for subtle clues like drifts and cornices covered by a few inches of soft snow to identify possibly wind-loaded features. While these types of avalanches are becoming much harder to trigger, there’s still enough uncertainty across the zone to keep us from ruling them out. 

    (2/9/2023)

    This uptrack test on a wind loaded slope produced obvious cracks. 

    Photo: Susie Glass

Avalanche Discussion

Saturday’s nice weather will make a pretty inviting day to be in the mountains. It will also be a bit of a transition day for the snowpack as lingering storm layers heal, while sunshine drives newer hazards. Often these are great days to push into higher terrain or bigger objectives. These are also the same places where we have the least information to support the forecast. 

On Friday observations from the White Pass and Crystal Mt backcountry indicated weak snow near the 2/3 interface. While no new avalanches were observed on this layer, snowpack tests continue to call into question the potentially weak structure. While some clouds prevented a more widespread loose cycle, observers did note new rollerballs and a few small loose wet slides. 

If you dig, consider all the new snow above the 2/3 crust/interface. This is often located 1.5-2.5 ft (45-75cm) below the surface. At lower elevations, significantly less new snow this week should limit the size and hazard of any avalanches. 

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