Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Avalanche danger will increase as snow accumulates and winds elevate. You could trigger avalanches in shallow pockets of wind drifted snow, or there is the possibility of triggering a deeper avalanche on northerly upper elevation slopes. Your best way to avoid any of these avalanches is to search for thicker, wind drifted snow deposits and steer clear of these areas on steep slopes.  

Problemi valanghivi

  • Wind Slabs

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

    Remain alert as more wind slabs will develop throughout the day, especially in the afternoon. You could trigger avalanches in these slabs. Most will probably remain shallow, less than a foot deep, but there is a chance that you could trigger a larger one at about two feet deep, especially if it involves a persistent weak layer (see the next avalanche problem). 

    Search for thicker, heavier drifts of snow and pillowy or textured surfaces. They’re oftentimes found on convex rolls, in gullies, and around rocky outcroppings. Steer clear of slopes steeper than 35 degrees where you encounter these wind slabs.

    (12/29/2021)

    At or just beneath rollovers or cornices at the top of a slope are spots that wind slab avalanches oftentimes break at. 

    Photo: Greyson Herdman

  • Persistent Slabs

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

    Two avalanches were remotely triggered at the beginning of the week in isolated pockets. Information is limited, but it is suspected that they failed on a layer of faceted (weak, sugary) snow above the late January crust. You are most likely to find them on the upper reaches of near treeline, and above treeline on east, north and west slopes. They will probably occur in wind-loaded areas. It is unknown how widespread this layer is, and we suspect the cover is inconsistent, making it more difficult to find. 

    Just because you made it safely down a slope in one spot, that doesn’t mean the whole slope is safe. If you notice whumphs and long shooting cracks they are clear indicators of unstable snow. Be wary around large, unsupported rolls on shady slopes, especially if wind loaded. Consider avoiding these areas as more weight is added to the snowpack.

    (2/1/2022)

    A small isolated pocket was remotely triggered by a snowmobile in the Canyon Creek area at 5500 feet on a northerly aspect. A persistent weak layer above the late January crust was likely the culprit.

    Photo: Mike Trowbridge

Avalanche Discussion

Thursday's storm produced less snow and fewer avalanches than we thought we’d get. Models align more for Friday's weather forecast, where we expect to see 6+ inches of snow falling during the day, and winds increasing to strong. This snow will add onto the 3 inches of water, or 18 inches of snow, since Saturday night at the Heather Meadows Weather station. A lot of uncertainty exists as to how widespread or reactive the persistent weak layer beneath this week’s snow is, but once we reach a critical additional weight (more snow) on the snowpack, we may see more avalanches failing on the layer. Keep this in mind if you’re in the backcountry while it’s snowing and blowing.

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