Boletín de aludes

Stevens Pass

Northwest Avalanche Center
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Peligro de aludes

Tue
Alta montaña
4 · Fuerte
Límite del bosque
4 · Fuerte
Bajo el límite
4 · Fuerte
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Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Very dangerous avalanche conditions are expected to develop on Presidents Day, and could last well into Tuesday. New snow, gradually warming temperatures and strong winds will create widespread storm instabilities, and rain at lower elevations could make for large wet loose avalanches. Stay off of and well out from underneath steep slopes as a potent winter storm rolls through.

Problemas de aludes

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Very Likely
    Tamaño
    1.5–2

    Expect storm slabs to build in size and reactivity during the day as moderate to heavy snow falls with a gradual warming trend.  Strong winds in exposed locations should only add to the potential size of slabs with the new snow. Cracking in the new snow and fresh crowns on small steep convex slopes are all indicators that storm slabs could be easily triggered or run naturally. 

    Stay off of and well out from underneath steep slopes as the storm creates unstable snow on Monday. You might be able to trigger slides from a distance and from below, and at some point tomorrow afternoon into thethrough the night we're likely to see a natural avalanche cycle. Many of these could be large and run long distances. 

    (12/20/2022)

    Example storm slab avalanche from earlier this season.

    Photo: Alexa Cathcart

  • Loose Wet

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

    Warming temperatures should turn snow to rain below treeline during the day, and kick off a round of wet loose avalanches. As snow surfaces become moistened and sticky, they could entrain into slides that pack a punch on steep slopes. This includes summer trails like the PCT that cut through steep slopes. Avoid going on or beneath steep slopes below treeline, as slides could run naturally and become large.

    (2/7/2023)

    Example wet loose avalanches at lower elevations.

    Photo: Jonathan Spitzer

  • Deep Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2–3

    A thin weak layer resting on a slick crust from mid-January is anywhere from 3-5ft down in the snowpack. We've been continuing to find test results that indicate propagation potential on this layer, and it keeps getting deeper. The last activity we know of on it was from February 8-13th. Some of these were quite large and surprisingly wide. With the incoing storm, we may see more activity begin to occur on this deeper weak layer. The resulting avalanches could be very large and destructive. 

    Avoid runout zones with large, overhead avalanche paths as a strong winter storm begins to stress this layer.

    (2/12/2023)

    Very wide crown spanning most of the south face of Jove Peak. This slide very likely occurred during the middle of the day on Sunday.

    Photo: Public Obs

Avalanche Discussion

With the incoming winter storm, we're expecting a widespread natural avalanche cycle Monday afternoon that could last through the night and into Tuesday. We could see multiple flavors of avalanches, all described above. Travel in avalanche terrain is not recommended while the storm rolls through. Avalanche danger is not expected to decrease rapidly even after the storm abates on Tuesday.

As of this writing, the pass has picked up 7-12" of new snow since Friday. These amounts are expected to turn into feet over the next 48 hours. Observers reported easily triggering small wind slabs above 5,000ft on Sunday, with rapid wind loading and steady snowfall. Dry loose avalanches were also easy to trigger on steeper slopes. Large column tests have continued to indicate the potential for avalanches to propagate on the MLK crust. This layer is now 3 to 5ft below the surface. Time will only tell if we'll see the snowpack connect the holidays with avalanches on Presidents Day running down to the Martin Luther King Jr Day crust.

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