Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

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

Enjoy the dreamy white Christmas, but recognize that you could trigger avalanches of various shapes and sizes. Large wind slabs can be found on open, wind-exposed slopes. Loose avalanches may be easy to initiate in sheltered areas. Don't let the avalanche grinch ruin your holiday by letting your guard down on steep slopes.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2

    You'll find wind slabs from the past few days as you gain elevation. Thursday into Thursday night was the main wind event, and created some very thick slabs in many areas. This could be tricky because slabs could be fresh, or they could be disguised underneath recent snow that fell without wind. Look and feel for thicker drifts, textured surfaces, and shooting cracks. You are most likely to trigger one on steep slopes near and above treeline in exposed locations, such as the leeward sides of ridges and near rocky outcrops. Avalanches could be larger at upper elevations, where there is more snow and drifts are deep.

    Avoid suspect-looking areas and likely starting zones such as convex rolls and pillowed snow on steep slopes. Stay off of steep slopes altogether if you find evidence of instability such as shooting cracks or the snow feels hollow or punchy.

     

    (12/19/2021)

    A crown from an avalanche (size D2.5) that ran on 12/18. NW aspect in the Chiwaukum range.

    Photo: Matt Primomo

  • Loose Dry

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

    The new snow is getting deeper, and may run fast on steep slopes. Look for signs of sluffing such as recent fan-shaped avalanches. These are also known as point releases, because they sometimes start at a single location, but can entrain more snow as they continue downhill. These can run naturally during periods of heavy snowfall, and are most likely to occur in areas where the new snow is deeper than about a foot. If you choose to enter steep slopes even outside of wind affected areas, travel defensively, as these slides could gain momentum and run far. If a slab fractures out, the slide could be much wider and larger than anticipated. 

     

    (12/23/2021)

    Loose dry avalanches ran easily on steep, wind sheltered slopes near Lake Wenatchee on Thursday.

    Photo: Nate Hough-Snee

Avalanche Discussion

Happy Holidays! The recent storm cycle that began on the Solstice has laid down a blanket of new snow with varying depth depending on proximity to the crest and wind distribution. Areas near the crest may have 30" or more over a thin crust from the 21st. Areas near Blewett Pass and Mission Ridge may only have around 6". Storm totals will continue to pile up Friday night into Saturday, and the SW portion of the zone such as Salmon la Sac will be favored.

On Thursday, winds were strong, and a number of observers noted lots of wind drifting within the new snow. Some even reported finding signs of wind slabs below treeline. Outside of wind-affected areas, observers above Lake Wenatchee easily triggered long-running sluffs on steep slopes within the new snow. 

The snowpack is generally strong and gaining depth near the crest, but shallow and weaker in the Wenatchee Mountains near Mission Ridge. There may be a layer of buried surface hoar on a melt-freeze crust (from 12/21) near Lake Clara/Mission Ridge. This layer may not be very widespread, but it's something to check for with quick pits if you head out to that area. In these easternmost areas of the zone, basal facets (weaker snow) may also be found near the ground. This weaker structure may become problematic in the future with new snow and wind loading.

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