Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 6 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Avalanche danger will increase as you gain elevation into areas where there are stronger west winds and loose snow to drift into fresh slabs. Avoid steep slopes that are accumulating wind-drifted snow. Anticipate a change to more wintry, colder conditions and continued snowfall in the coming week.

Problemi valanghivi

  • Wind Slabs

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

    Modest amounts of new snow in the forecast shouldn’t add much to avalanche danger on their own. Adding wind to the picture is another story. At mid elevations, the only snow available for transport should be what falls after rainfall switches to snow early in the morning. Slabs at those elevations might be reactive, but not very big. At upper elevations, colder temperatures have kept the snow surface drier, allowing it to drift more easily and for wind slabs to grow thicker.

    Monitor changes in new snow depth and stiffness as you gain elevation or switch aspects. Test slopes and hand pits can help you gauge the bond of new wind slab layers, but the safest bet is to avoid steep slopes on the receiving end of blowing and drifting snow.

    An added complication is that a small wind slab avalanche could trigger a larger slab failing on older weak layers buried deeper in the snowpack. Canyon Creek and other areas north of Highway 542 are most likely where this is an issue, but less-traveled terrain could have a similar setup.

    (4/9/2022)

    Stiff, slabby snow? Check. Cracking? Check. Wind-affected surface? Congratulations, you found a wind slab!

    Photo: Dallas Glass

Avalanche Discussion

Wet snow and poor riding conditions kept backcountry observations to a minimum on Saturday. The few who were out reported the snow surface simply became wetter with light rainfall, but no new wet avalanches or other signs of instability were noted as of late afternoon.

An NWAC forecaster in West Central near Darrington found overall wet conditions on Saturday, with no dry snow at the surface up to about 5500 feet. Numerous rollerballs and one wet avalanche, about D2 in size, had released in the past 24 hours, likely overnight when rainfall was heavier and more consistent. Rollerballs and small wet snow avalanches very stubborn to trigger. About 2 feet of moist snow sits over crusts from late January and early February, but snowpack tests revealed no layers of concern.

The persistent slab problem from last week was never consistently observed across the forecast zone. Time, warm temperatures, additional loading from rain and snow, and a lack of recent avalanche activity and significant snowpack observations have taken this problem off the table. However, deeper layers could still be triggered by large loads, such as a small avalanche or a falling cornice, even though a single person would be very unlikely to trigger one. These are low-likelihood events, but something to keep in mind if heading into less-traveled terrain or areas where persistent slab avalanches were reported last week.

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