Boletín de aludes

Snoqualmie Pass

Northwest Avalanche Center
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Peligro de aludes

Fri
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 5 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Take note of how the snow surface is changing throughout the day as Snoqualmie Pass is impacted by rain, wind, and snow showers. If you notice rain is falling on dry snow or the snow surface is wet and sloppy, head for slopes less than 35 degrees.

Problemas de aludes

  • Loose Wet

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

    On Thursday, look for the possibility of Wet Loose avalanches anywhere rain is falling on dry snow. This will be more likely on slopes that haven’t seen direct sunshine lately, particularly as you ascend in elevation. The caveat of course is that the rain line will only extend so high, so these slopes may be hard to come by. Natural activity often peaks near the onset of rain falling on dry snow, and if you are in the sweet spot where these avalanches are possible, you may notice fresh fan-shaped avalanche debris or rollerballing. Your best mitigation technique is to retreat toward lower angled slopes, keeping aware of slopes above you that could shed snow onto your travel route.

    (12/19/2020) An example of Small (D1) Wet Loose avalanches from earlier this season at Snoqualmie Pass during a rain on snow event.

Avalanche Discussion

Snoqualmie Pass has had a largely aspect-dependent snowpack the past few days as sunny days and cool nights have created melt-freeze cycles on slopes that see direct sunshine. This has created firm surfaces in the mornings which have softened throughout the day, resulting in small Wet Loose avalanches or rollerballing activity. On slopes that haven’t seen direct sunshine, the snowpack has been more cold and dry, with wind-pressed surfaces or unconsolidated snow depending on your location. As we move into a more active weather pattern, be sure to check the bonding of any new snow to these various snow surfaces by using test slopes or hand pits before stepping into consequential terrain. 

On Thursday, slopes that have not been through multiple melt-freeze rounds may contain the higher potential danger below the rain/snow line. We have a little bit of uncertainty around where the rain/snow line will end up, but it will be easy for you to determine while you’re in the field. As you travel above this line, new snow totals should be minimal, but you could find some freshly built shallow Wind Slabs to steer around. Look for these to possibly exist on leeward slopes near ridgelines or near rocky features such as cliffs and gullies. In some locations, they could overlay some weak snow grains and result in shallow but surprising avalanches. 

A lot of Glide cracks have opened up around Snoqualmie Pass during the recent warm weather. Although cracks don’t necessarily mean avalanches, adding liquid water to the snowpack could help larger chunks of snow such as Glides or Cornices to fail. Continue to be cautious around these features, especially if it is raining.  Although it may seem like we have made the transition to a springtime snowpack and winter is behind us, we are not there yet. Plenty of cold dry snow and layers of concern still exist in the mid to upper snowpack and this upcoming weekend should be more winter-like than spring-like. 

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