Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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In sintesi

With cooling temperatures, wind, and light snow, you could still trigger avalanches in the new and recent snow. You're most likely to trigger avalanches in shallow, fresh wind drifts at upper-elevations. However, avalanches in older snow layers are also possible in wind-sheltered terrain. Stick to low-angle slopes if you observe warning signs such as shooting cracks, recent avalanches, or collapsing. 

Problemi valanghivi

  • Wind Slabs

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

    Watch for actively drifting snow, shooting cracks, or stiff snow over softer layers as signs of reactive wind slabs. Ridgelines, confined rocky terrain features, and cross-loaded gullies at upper elevations are the most likely places to encounter this problem. Choose sheltered terrain or steer around steep slopes with deep drifts to avoid triggering avalanches. 

    The recent warm temperatures and rain up to upper elevations suggest that most avalanches will remain small within the fresh snow. However, before committing to steep, consequential terrain, be prepared to assess wind-drifted snow for depth and reactivity. 

    (11/29/2024)

    Wind drifted snow on a ridge in the Hairpin Valley.

    Photo: Katie Warren

  • Storm Slabs

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

    While we expect most storm slab instabilities to be settled out, there are lingering concerns in the eastern portion of the zone. Collapsing, shooting cracks, and recent avalanches are all signs you should avoid steep slopes. Use small test slopes and roadside cutbanks to check for any of these signs before committing to larger, steep terrain. 

    Recent observations of avalanches failing on buried weak surface hoar on Thursday in the eastern part of the Twisp River indicate that some isolated areas still harbor avalanche concerns in sheltered terrain. This problem may be extremely isolated to the Blackpine Lake area or extend further west into the Twisp River and north into the eastern foothills. We have a lot of uncertainty regarding the distribution, but evidence suggests it's not a widespread problem in the Highway 20 corridor or Hart's Pass area. If you're traveling in more remote, eastern parts of the zone, dig down and identify the grey line in the snowpack that clearly identifies these problematic surface hoar layers. 

    (12/26/2023)

    An example of buried surface hoar within the snowpack. 

    Photo: Katie Warren

Avalanche Discussion

Cooling temperatures and light snow should help reduce lingering wet avalanche concerns throughout the zone. Although lower elevations may take longer to cool and small, isolated wet avalanches might still be possible. 

On Friday, observers in the Highway 20 corridor reported rain up to 7,500 ft, and snowpack tests showed that storm snow interfaces from earlier in the week were strengthening.  

Observers near Blackpine Lake on Thursday reported small avalanches failing on a layer of buried surface hoar. While the distribution of this problem is uncertain, it's evidence that the eastern portion of the zone may hold a more complex snowpack with avalanche concerns that could linger for an extended period of time. Pay attention to red flag signs of instability, such as whumping collapses, and consider digging down to identify weak snow layers before committing to steep slopes. 

The Washington Pass area saw around 2 feet of snow from 12/17-12/18, along with a widespread natural avalanche cycle. On Wednesday, an observer in Mazama reported storm snow totals of 36" and wet loose avalanches. An observer on Blue Lake Peak reported numerous large to very large natural avalanches that ran Tuesday night, and they experienced snowpack collapses. Observers near Frost Lake also reported collapsing and plumes of blowing snow on the ridge of Oval Mountain. Snow water equivalent storm totals from weather stations likely only tell part of the story. Rainy Pass: 3.4" SWE, WA Pass:  1.7" SWE Mazama 1.7" SWE. 

You can contribute to the avalanche forecast. Please let us know what you see in the mountains by submitting an observation. 

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