Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

South-facing slopes will soften for one more day, and wet snow avalanches might occur from late morning. When you start sinking past your ankles into the snow or see rollerballs running down a slope, shift to firmer surfaces. You’ll find more supportable snow on lower angle slopes or in northerly terrain where hard, bumpy surfaces exist.

Problemi valanghivi

  • Loose Wet

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

    Saturday wet loose avalanches occurred midday, many of which started near steep, rocky outcroppings, but fanned out on large slopes beneath. These were mostly in the small size range, but some were nearing large in size. Expect similar conditions through midday Sunday. Increasing afternoon clouds could slow the trend later in the afternoon on more westerly slopes. 

    A major player in how soft surfaces are getting is the angle of the slope relative to the sun. The more direct of an angle, the more the snow will soften and get wet. Low angle or flat surfaces are not softening much, but shift just a little to steeper south-facing terrain and all of a sudden you’ll find much softer snow by about 10am onwards. The surface may break down enough so that you’ll sink through the loose, moist layer beneath, all the way to the late January crust around a foot deep. Before this starts happening, shift off the steep, sunny slopes. If you see avalanches or rollerballs, stay off similar slopes as well.

    (2/12/2022)

    Recent loose wet avalanches on East Goat in the Upper Nooksack. South aspect at ~6000ft. 

    Photo: Lee Lazzara

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1.5–2.5

    Forecaster Lee Lazzara investigated the Persistent Weak Layer on Saturday. He found that it still exists on upper elevation slopes on the northerly half of the compass. In these areas, the warm, wet weather softened just the surface, forming a thin, breakable crust on northerly terrain. The underlying layers are still dry and minimally affected. He found a recent isolated avalanche which probably failed on the persistent weak layer on a steep, north-facing slope of Table Mountain at about 5500ft in the Baker backcountry. 

    If you’re on steep, north-facing terrain at upper elevations, pay attention to how thick the surface crust is. Where the crust is thinner (an inch or less), the weak layer may still exist at about two feet deep, just above the Late January Crust. So far, we’ve found that you can get away with traveling on many steep slopes without causing an avalanche, but there is a very small chance that you could trigger an avalanche on that layer if you find just the right spot on the slope. It’s important to consider this if you’re planning on heading to steep upper elevation northerly terrain, as you might be taking a bit of a gamble on steep slopes.

    (2/12/2022)

    Large (D2) natural slab avalanche on a north aspect of Table Mt at ~5500'. This is suspected to have released in the late January crust-facet layering. 

    Photo: Lee Lazzara

Avalanche Discussion

Stay alert for large cornices baking in the sun. A cornice fall itself would be scary, but it also could be a large enough trigger for an avalanche on the persistent weak layer if it’s on the right slope. Give large cornices a wide berth.

Sunday night will rapidly cool to a freezing level of 3000ft by Monday morning. We’ll receive a burst of snow early Monday, amounting to 3-6 inches, just enough to pad the hard surface. Until then, beware of the firm, variable surfaces present in most areas.

Regioni coperte