Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Limite del bosco
2 · Moderato
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1 · Debole
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In sintesi

Wind slabs from the 5-10" of snow we received with wind on Wednesday could avalanche with a human trigger, especially as you gain elevation and find deeper wind drifted pockets. Search for smooth pillows and textured surfaces, or long cracks shooting from your feet, and steer around steep slopes when you notice these characteristics. Expect to see wet loose avalanches on steep south-facing slopes as the day heats up, which are areas to steer around when you start seeing copious amounts of rollerballs running down. 

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Wind slabs up to about a foot deep could exist on top of the MLK crust. In areas where the snow was redistributed by the wind and became stiffer, it's possible that you could trigger an avalanche, maybe running down to the crust. In the neighboring West North zone we received reports of avalanches which failed naturally during the end of the storm on Wednesday. The two avalanches propagated surprisingly far, and we suspect they may have failed on a buried persistent weak layer just above the crust. There could be a weak layer above the crust in this zone too, but at the time we don't know much about it or whether it's continuing to be a problem. 

    On Friday, some people will probably find and trigger slab avalanches on this beautiful day. Start on small slopes before you move out to larger terrain. Use test slopes (see video below) and hand pits to check if there are any lingering weaknesses above the crust. Conveniently, the crust is buried shallowly and is obvious, so it should be easy to test the snow above it where our suspect weak layers are. Your largest areas of concern are where wind loading formed slightly stiffer slabs. As is the case with the recent West North avalanches, a likely location for reactive slabs to form is around cliff bands, where thicker drifts can form, or snow piles up deeper. They could also form on leeward slopes just below ridgelines and in gullies.

    If you're stepping out onto steeper terrain, make sure you've got an escape route planned if a slope slides. Think twice before stepping onto slopes with high consequence, like ones with trees or rocks below, or ending in an abrupt gully. If you identify any signs of instability, see large wind-loaded features, or have any doubt, avoid slopes steeper than 35 degrees.

    (1/19/2023)

    Wide-spanning natural D2 slab avalanche which likely occurred in the tail end of the storm 1/18 afternoon. Wind-effect is noticeable in the area. West North zone, similar but probably larger than what you might encounter in the West Central zone. S, 5200ft SS-N-D2-I 

    Photo: Robert Hahn

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    We don't suspect much wet loose activity occurred Thursday, as it stayed relatively cool despite the blue skies.  There was just enough sun that Friday may start out with a slight crust on steep, sunny slopes. Freezing levels are reaching much higher on Friday, to 4000ft, with minimal wind. As the sun intensifies, you'll probably see indicators on steep, south-facing slopes first, like rollerballs coming down. Snow might get sticky, or gloppy. When this starts happening, pay attention to where you are, and where you're going. You may need to change your plans to avoid steep south-facing slopes, or beneath those slopes as well if wet loose avalanches start running in the new snow layer. The problem may shift a little further to the west as the day progresses. Avalanches will probably stay shallow and in the top few inches, but depending on how much warming we see, they could take up much of the depth of the new snow.

    (11/24/2022)

    Rollerballs like this are often indicators that the snow surface is becoming weak and wet loose avalanches may soon follow.  

    Photo: Robert Hahn

Avalanche Discussion

On Thursday in neighboring zones, you could trigger shallow dry loose avalanches on shady steep slopes on Friday. Don't send them down on a companion, or get caught in one that you trigger, especially if you're near terrain traps. 

Our most recent storm Wednesday and Thursday produced just under a foot of snow in the zone. It was a welcome new layer, although mid and lower elevations still have shallow spots and holes that may sneak up on you in your travels.  Saturday we're expecting a small yet intense burst of snow with strong winds to spice up the weekend. 

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