Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Wed
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

You can still trigger an avalanche in wind drifted snow at and above treeline. Identify and avoid areas where the wind created deeper, denser drifts to reduce the likelihood of triggering an avalanche. 

Problemi valanghivi

  • Wind Slabs

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

    Backcountry travelers triggered a handful of small avalanches and one larger wind slab over the weekend. It’s not unusual to trigger smaller pockets of wind slab a few days or more after the last wind loading event (in this case December 2nd). It's a bit less common to see a larger wind slab avalanche in that same timeframe. 

    You could trigger one of these in very steep unsupported terrain like convex rollovers, above or around cliffs, and under cornices. Be on the lookout for rounded, pillowy-looking drifts perched over steep terrain. A few inches of new snow, moderate winds and less visibility on Tuesday could make areas of wind slab harder to identify and maybe build shallow new slabs.

    Snow pits and other quick tests might give you more information to judge stability. You can also just avoid the problem by using a lower angled line to navigate around suspect features. There is plenty of usable terrain where you won’t trigger one of these - you just need to identify the few places where it is still a very real possibility.

    Example of a wind drift indicating the direction of loading.

Avalanche Discussion

Cold and clear weather persisted for West North over the weekend. Southeast through southwest facing slopes warmed enough to create rollerballs and even a few very small wet loose avalanches. Slightly elevated freezing levels did little to warm north facing terrain. While a hard breakable crust now coats solar aspects, shady slopes still hold soft snow where not wind affected.

Near treeline there is generally 2-4 feet of settling snow over a rain crust buried on Nov 25th. Below are alternating layers of rounding facets and hard crusts to the ground. Cold temperatures have likely drawn out both the settlement and rounding processes compared to average conditions. Weaker interfaces between recent storm and wind slab layers usually bond quickly - with the typical near freezing temperatures. Currently, the same layering appears to be staying weaker for longer in this colder weather pattern.

The current structure is not yet alarming and may never be a widespread problem. A lack of consistent avalanche activity demonstrates the snowpack is mostly handling the current load. On the other hand it’s not a status quo snowpack for early December. Keep this in mind and take the extra time to investigate and get a feel for the snowpack where you travel. 

Regioni coperte