Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

Heavy snowfall is expected overnight and into the morning. Avoid steep, open slopes or any avalanche terrain with terrain traps like trees, rocks, or gullies in the runout. Dangerous avalanche conditions will persist through the weekend with more storms and warming temperatures.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2.5

    Backcountry travelers triggered multiple slab avalanches up to 1’ deep around Heather Meadows on Friday. Expect more of the same - or deeper - on Saturday. The biggest slabs will be found in wind loaded areas, but all terrain should be on your radar.

    It’s basically a day to avoid most steep terrain. This is due to the amount of new snow, recent avalanche activity, and uncertainty about our variable snowpack. Layers of weak, faceted snow were found to be a player in avalanches reported from multiple forecast zones, West North included.

    Some natural avalanches are expected in terrain seeing continued heavy snowfall and/or wind loading. Natural avalanches are more likely in the morning but should be in the back of your mind all day. Keep an eye on what is overhead and minimize your exposure to steep terrain.

    (12/28/2020)   

    Example of a large slab avalanche with a 1'-2' deep crown on Shuksan Arm.

    Photo: Colin Wiseman

Avalanche Discussion

The peak of instability and natural avalanche activity should occur overnight or early in the morning when the storm is at its peak. Areas that see continued heavy snowfall and strong winds could see more natural avalanches and higher overall danger.  

Soft slab avalanches were easy to trigger in steep mid-elevation terrain on Friday, but more than one observer noted that hand pits and small test slopes showed little in the way of instability. They had to actually get into steep terrain to find out if they could trigger an avalanche. While wind transport was noted in some areas, avalanches and other signs of instability were found on slopes with few signs of wind loading.

The biggest question mark is the extent of faceted snow at and below the 11/30 interface. In other zones it is quite widespread, making for a weak and concerning snowpack structure. Faceted snow was also found on the bed surface of some avalanches triggered today in West North. No matter how widely it's distributed, the old snow surface adds an extra layer of uncertainty and is cause for a more conservative plan if you want to avoid avalanches.

Heather Meadows picked up about 1’ of light-density new snow from 0.85” of precipitation in the last 24 hours. Other parts of West North saw comparable snowfall. Winds gusted to strong overnight but backed off a touch through the day. Temperatures stayed cool and snow quality remained good if you weren’t put off by some crust under the new snow in some areas.

Lower elevations hold little to no snow, though an inch or two of snow fell as low as Glacier on Hwy 542. Travel at mid-elevations is improving but the snowpack is still thin with plenty of hazards to ruin your day. New snow will barely hide some early-season hazards that were clearly visible in recent weeks.

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