Boletín de aludes

West Slopes North

Northwest Avalanche Center
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Peligro de aludes

Wed
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 3 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

A shot of southeast wind will keep the mountains cooler but build fresh slabs of wind drifted snow. Avoid steep slopes where you witness active wind loading or that hold smooth, fresh-looking drifts. If you start seeing natural avalanche activity take a bigger step off and away from wind loaded slopes. Don’t forget about wet avalanches on sunny slopes at lower elevations or where the wind isn’t blowing.

Problemas de aludes

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    Strong winds should keep wet loose avalanches in check Tuesday, except of course where there is no wind. The likelihood is lower and the size will be smaller but keep track of what’s going on above you if it's calm and warming up. Lower elevations are where these avalanches are more likely to occur, but it’s spring and wet avalanches could be a thing anywhere on any given day. 

    On a side note, a cornice failure was observed today out on Coleman Pinnacle in the Baker Backcountry, yet another sign spring is here. The likelihood of these failing will vary from day to day based on temperature, sun, etc.  Either way, it's time for them to start falling down. Give big cornices plenty of room and anticipate the consequences if one falls down and triggers a larger avalanche.

    Example of small loose wet avalanches on short but steep slopes.

    Photo: Julz Holder - Grounding Truth

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Wind slab formation Tuesday will be dependent on a few things. One is the amount of snow available for transport. The slopes providing most of the snow have some amount of crust on them. That could limit what can get blown onto leeward slopes.

    Southeasterly winds also often come with an unusual pattern. Some mountains and ridges will see sustained strong winds while other areas might remain calm. There will likely be stronger winds farther east in the zone but be ready to see them anywhere. 

    Finally, there is surface hoar and faceted snow at the surface on northerly slopes. Though fresh wind slabs will be fewer in number and size, what you do find might be more reactive than normal.

    Blowing snow will be the main observation to identify areas of active wind loading. Test slopes and hand shears will help gauge slab reactivity and depth. You may see slabs form farther downslope or on different aspects than usual.

    Example of a small, human triggered wind slab in alpine terrain.

    Photo: Zach Bunch

Avalanche Discussion

A wide range of avalanche activity was observed around Hwy 542 since the last storm. In addition to numerous natural and human triggered wet loose avalanches, human triggered slab avalanches to D2 were reported through Sunday. It appears most of them failed at an interface within the new snow based on crown depth. A handful of larger, natural slab avalanches that released during the storm were also observed.

The current snowpack question mark is a layer of weak, faceted grains that sit below the new snow but above a crust that formed on all aspects about a week ago. In most places they were dispersed by strong winds prior to the last storm, but not in all. Though no avalanches were directly linked to this layer, reports of whumphing, test results showing propagation and a slightly unusual pattern of avalanche activity warrant a bit more caution, especially in terrain with cliffs, rocks, or other terrain traps in the runout. 

Solar aspects are topped with some variation on sun crust. Some shaded slopes also have a soft crust near the surface, probably due to a period of greenhouse conditions over the weekend. The same weather setup may have contributed to periods of increased slab avalanche activity.

Anywhere from 1’-2’ of new snow fell across West North from March 23rd-25th. Subzones on the west end of Hwy 542 may have picked up the most due to a switch to westerly flow part way through the storm. Heather Meadows received 16” during the meat of a storm with a few more on Saturday. 

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