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
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Clearing skies and fair weather will shift our main avalanche concern to wet snow problems, especially on sunny slopes as temperatures warm throughout the day. If you notice rollerballs running down a slope, or heavy and wet snow surfaces then avoid traveling on or beneath these areas. On shady slopes especially at upper elevations, wind may have redistributed light snow into thicker, reactive deposits, something to avoid on Sunday as well.

Problemi valanghivi

  • Loose Wet

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

    Freezing levels are forecasted to rise to 7500 feet Sunday afternoon. Skies may actually clear for a day before clouds return. This, in combination with low-density surface snow from the last few days (about 6-10 inches reported Saturday and a couple more Saturday night) primes us for wet loose avalanches. Clear skies will probably limit the problem to sunny slopes, but if clouds develop, wet loose avalanches could run on all aspects. 

    Pay attention to snow surfaces as you travel. If the snow begins to get wet and clumpy, and if you notice rollerballs or small wet loose avalanches running down a slope, steer clear of similar slopes and the runouts beneath them. They will probably remain limited to the low-density surface snow. Depending on how warm it gets, they could fan out and become large enough to catch and carry you or cause more damage if you’re near a terrain trap. If they’re running on sunny slopes, consider shifting to shady, more northerly aspects where you may not find that problem.

    Glide avalanches could come to life as temperatures increase and water percolates through the snowpack. This is especially the case on sunny slopes with smooth underlying rock or grassy surfaces.

     

    Rollerballs currently rolling down a slope like this indicate the surface snow is becoming wet and unstable.

  • Wind Slabs

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

    Low-density snow in some upper elevation areas shifted into thicker wind slabs in recent days and overnight. It is possible that you could trigger an avalanche on these slabs. These avalanches could stay shallow, only a few inches, or might be one to two feet deep. Search for textured snow surfaces, pillows, or firmer feeling snow. Keep an eye out for shooting cracks. Start on smaller terrain before stepping out onto larger slopes.  If you find any signs of wind-loaded snow, move to areas that are non- wind-affected or stay on slopes less than 35 degrees.

    (1/2/2022)

    A shallowskier triggered wind slab avalanche which occurred in the Baker backcountry near the beginning of this large storm cycle. 

    Photo: Matt Lubar

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    3

    In the West North Zone we are still suspicious of a layer of surface hoar buried on December 21st. It produced and a handful of very large avalanches centered around Shuksan Arm in late December. Some released naturally while others were triggered with avalanche mitigation work. We’ve had several storms since then and the layer is probably between 5 and 9 feet deep. These avalanches are very difficult for a single person to trigger. However, they could react to a large load like a falling cornice or a smaller avalanche stepping down and triggering a much larger avalanche at this layer. Be aware that large deep slab avalanches from higher terrain could run into lower elevations where avalanches are not normally seen.

    (1/1/2022)

    At the crown line of the deep persistent slab avalanche which occurred in the Baker backcountry on Friday 12/31. 

    Photo: Irene Henninger

Avalanche Discussion

We're wrapping up on a storm cycle that lasted from January 2-7, with a lull on January 5th. Over 7 inches of water fell at the Heather Meadows weather station.  At least 5 feet of snow fell at upper elevations, while rain during the second half of the storm came in at lower elevations, washing away some of the impressive lowland snow base.  Road travel has been challenging, weather stations struggled, and observations are limited due to accessibility challenges. There are a lot of things we don’t know about these new snow layers. We're just starting to get reports of avalanches which occurred during the storm- D2 and D3 (large and very large) avalanches were reported on Saturday, having failed on previous days. We hope to find out more on Sunday.  The snowpack is slowly stabilizing but continue to exercise caution with all these uncertainties in the conditions. 

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