Boletín de aludes

East Slopes Central

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 3 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Wet slab avalanches are becoming likely at low elevations, along with an increased threat of roof slides. In the Wenatchee Mountains, the warmup brings dangerous conditions for persistent slabs that could break across terrain features 2-3ft deep. Choose lower angle slopes for travel, and avoid going on or hanging out underneath large steep slopes as the snowpack undergoes a transition. 

Problemas de aludes

  • Wet Slabs

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

    Warming temperatures and rain on snow kicked off a round of wet slab avalanches on Monday. These slabs are likely to run on weak snow over the crust from back in December and could be 1-2ft deep. Wet loose avalanches are equally as likely to occur, and these may or may not trigger larger wider slabs. 

    Wet avalanches often start from trees or rocks shedding snow onto slopes below, but you can also trigger them with your skis or snowmobile. Look for signs of instability that include rollerballs, or fresh wet slides. It'll be a good day to limit your time spent underneath steep slopes where slides could run, especially if the snow is very wet and heavy.

    Roof avalanches have been releasing, so use a spotter if shoveling or spending time underneath a loaded roof. 

    (1/22/2024) Photo: Mike Rolfs

    Small wet slab ran with rain on snow on the Mission Ridge access road on Monday.

  • Persistent Slabs

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

    Multiple large, human triggered avalanches ran on the Solstice Crust at Blewett Pass on Saturday. The base of the snowpack in the Wenatchee Mountains very weak. Avoid avalanche terrain if you are traveling in the eastern portion of our zone, near Mission Ridge, Blewett Pass, or the Entiat areas. You could trigger one of these avalanches from low-angle terrain below or adjacent to steep slopes.Persistent slabs are a tricky problem, often leading to a false sense of security with no apparent signs of instability, such as collapses or shooting cracks. An unlucky individual could hit the wrong spot on a steep slope, and the whole slope may fracture and slide. It may not be the first skier or rider on the slope, but it could be the second or third. Your best strategy is patience and conservative travel choices. Give yourself wide safety margins around large open terrain and avoid steep slopes where a smaller avalanche could step down to these deeper weak layers.

    Further west, these slides have become more difficult to trigger. Although the weak structure still exists, it's just more deeply buried. If you got unlucky, you could still trigger an avalanche 2-4ft deep and could be surprisingly destructive. 

    (1/20/2024)

    This avalanche that failed on the Solstice Crust was triggered by a skier on Saturday on Diamon Head, Blewett Pass. Notice the older crown to the left in the photo.

    Photo: Brett Hlavka

Avalanche Discussion

Warm temperatures and rain continue to creep into the zone. Temperatures rose above 32 for the first time in a couple weeks in many areas on Monday, and that trend should continue on Tuesday. Many areas picked up 5" or so of new snow on Monday before the temperatures began their warming trend. Water amounts varied, but Mission Ridge received a whopping 0.8" of SWE overnight into Monday. 

I was out the past couple days in the far western edge and the eastern edge of the zone. Although the snowpacks ranged in depth from 150cm in the upper Icicle to only 100cm in the Blewett Pass area, there were certain commonalities that are worth discussing. First, there is a substantial amount of new snow since January began (2-3ft). Second, we could identify a weak structure near the base of the snowpack that consisted of faceted grains over and often beneath a weak, decomposed crust (2-3ft down). Third, snowpack tests showed the potential for avalanches to propagate on this layer in both locations.

The Solstice Crust in the Wenatchee Mountains has been active since late December and continues to produce avalanches. Human triggered avalanches on this persistent weak layer have occurred on Jan 6th, 12th, 15th, 19th, and 20th. On Saturday in nearby East South, a rider remotely triggered an avalanche near Manastash Ridge that we suspect ran on the Solstice Crust. While these avalanches have primarily occurred in wind-loaded terrain, we can't rule out triggering avalanches in sheltered areas, especially as temperatures warm up and change the snowpacks properties. 

If you get out, let us know what you see by submitting a public observation!

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