Boletín de aludes

West Slopes North

Northwest Avalanche Center
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Peligro de aludes

Wed
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Desactualizado: este boletín caducó 5 months ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

The foot of nice, dry snow that fell last week got heavy and then wet on Monday, resulting in a small avalanche cycle. More rain Monday night and Tuesday means we expect continued avalanche activity, with avalanches probably becoming less frequent but growing larger as time passes. Stay off steep slopes on Tuesday, and if you see natural avalanches, steer around the bottom of large steep slopes as well. 

Problemas de aludes

  • Wet Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1.5–2.5

    After the initial rain-on-snow event on Monday, we expect avalanche activity to slow. But temperatures are staying warm, and it'll continue to rain, so as water impacts deeper into the snowpack, larger avalanches could release. We suspect they will happen less frequently, but they could gouge deeper and run farther than the previous day.

    The avalanches that we saw Monday started as storm slabs, when heavier snow fell over the light, dry snow. By midday, as rain reached into upper elevations, wet loose avalanches probably began running down. At some point, wet slabs are expected to start releasing.  It's extremely challenging to predict when we'll start seeing these large, scary, and highly unpredictable avalanches. We think they'll really kick off Tuesday night when rain picks up, but they might happen sooner. 

    Avoid traveling on any steep slopes on Tuesday. If you see natural avalanches coming down, we've probably reach high danger, so steer around the bottom of avalanche paths as well. This is also a day to not linger beneath skinny, tight gullies, even at lower elevations that connect to higher-elevation terrain. 

    (1/27/2024)

    It's hard to pin down when, exactly, large wet slab avalanches to happen. If there are many like this on Tuesday, then danger is High. 

    Photo: Pete Durr - USFS

Avalanche Discussion

A little over an inch of rain fell in the central and western parts of the zone Sunday night and Monday, and further east, rain amounted to closer to half an inch. When heavier snow began falling Monday morning, an avalanche cycle ensued, consisting mainly of small storm-slab avalanches. Mid elevations transitioned to rain late morning, and we suspect there were subsequent wet loose avalanches. 

Around half an inch of rain is expected to fall Monday night, and similar amounts again during the day. There's about a foot of snow on top of the 3/12 crust, and by Tuesday we expect most, if not all, of that previously light, dry snow to be wet. As water eventually percolates down to the 3/12 crust and potentially lubricates above the crust, wet slab avalanches could run on the crust.

When rainfall amounts pick up Tuesday night, we expect a natural wet slab cycle, with lingering very large and highly unpredictable natural wet slab avalanches continuing into Wednesday. We don't think slab avalanches will step down below the 3/12 crust, but it's not completely off the table that an even larger, deeper one could happen. 

Expect challenging travel conditions on Tuesday, with rain and wet snow. 

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