Boletín de aludes

West Slopes South

Northwest Avalanche Center
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Peligro de aludes

Mon
Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 3 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Take note of how snowpack stability is changing due to the weather on Sunday. Depending on your location and elevation, snow, rain, or something in between will drive avalanche potential. When in doubt, avoid slopes over 35 degrees where you’re more likely to trigger an avalanche.

Problemas de aludes

  • Storm Slabs

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

    On Sunday, expect to find winterlike storm conditions above the rain/snow line. This will be especially true on the volcanoes where more precipitation is expected. Regardless of location, if you find more than 6 inches of new snow, start thinking about slab avalanches. If the prior surface is warm and wet, expect to find a fair bond. You can use quick hand pits as you travel to check this bond and look for potential points of failure. Small test slopes are another excellent tool to see how the new snow reacts to your weight. If you find a poor bond or that snow is failing in blocks, avoid slopes over 35 degrees.

    (1/19/2024)

    Two  natural storm slab avalanches that likely failed on the 1/16 interface. NNE 6100ft. Similar avalanches could occur on Sunday.

    Photo: White Pass Ski Patrol

  • Loose Wet

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

    The highest chance for wet avalanches is in locations where rain falls on dry snow for the first time. Areas such as White or Chinook Pass that have remained relatively cold in recent days come to mind as examples of where wet avalanches may be more prevalent. That doesn’t mean they can’t occur elsewhere, however. These slides often start at a point and fan out as they descend, possibly growing large or triggering slabs in the process. Avoid steep slopes over 35 degrees if you see new rollerballs and pinwheels, fan-shaped avalanche debris, or rain falling on dry snow.

    (1/19/2024)

    Rollerballs like this show that the surface snow is becoming wet, sticky, and potentially unstable. 

    Photo: Andy Harrington

  • Deep Persistent Slabs

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

    This warm system will continue to stress our snowpack and deeper weak layers. Snowpack tests on the Solstice Crust matrix remain concerning. And we are still discovering very large avalanches every few days as we scan the landscape around the West South. This problem exists throughout the zone and should shape your travel plans. Minimize the amount of time spent in big open terrain where one of these slides can start, run, or stop.  

    (1/19/2024)

    A very large (D3.5) natural deep slab avalanche near The Cowlitz Chimneys. Other smaller (D2.5) deeper avalanches were also observed in the area.  E, 6600ft. 

    Photo: Andy Harrington

Avalanche Discussion

Our transition from cold and dry to warm and wet will continue on Sunday. Expect a smorgasbord of precipitation types, including rain, snow, freezing rain, and sleet. Variability is the name of the game right now - variable weather, variable surfaces, variable snow depths, variable layers of concern, and variable avalanche problems. 

Almost every type of avalanche problem occurred in the zone this weekend. Wet and dry avalanches (both slab and loose) were observed on Friday as temperatures rapidly increased and rain fell. The exception was the mountain passes, where cool easterly flow kept precipitation primarily solid. Observations are limited from Saturday, but a public observation from Paradise noted additional slabs and debris piles from what was reported on Friday. 

Heading into Sunday, we now have a variety of surfaces for new snow or rain to fall on. Rain crusts can make a great sliding surface for storm snow. Conversely, a warm and wet surface will allow for a favorable bond for incoming snowfall. Additional rain may help snow shed from rocky ledges or unsupported slopes at lower elevations. The transition zone between rain and snow in middle elevations may be the most dangerous, where competing weather factors could result in unusual avalanches.

The Solstice Crust continues to be our main focus in the snowpack, but other layers, such as the 1/16, could be active during this period. The distribution of this layer is a bit spotty, but weak facets were found at this interface prior to the warmup. It could produce some widely breaking avalanches in areas where it hasn’t already gotten wet or been overloaded with new snow. 

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