Bollettino valanghe

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Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto last year. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You can still trigger a large avalanche in wind-stiffened snow. Steer around steep and unsupported slopes below fresh, sharp cornices and where you encounter punchy layering. When the sun comes out, expect recent snow to shed off rocks, cliffs, and produce small avalanches on the slopes below.

Problemi valanghivi

  • Wind Slabs

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

    As the storm relents by Saturday morning, you're more likely to trigger a slab where recent winds have been depositing snow. Note the subtle sharp cornices overlying wind-loaded slopes, textured snow, and the slopes opposite the scoured sides of ridges to identify the steeper slopes you'll want to steer around. You may also encounter firm over weaker snow layering or cracking as indicators that wind slabs are forming in your terrain.  Note that any avalanche you trigger has the potential to entrain lots of recent low-density snow that can move you significant distances into trees, over cliffs, or into terrain traps.

     

    (3/21/2025)

    Large rider-triggered avalanche on the 20th of June slide Path. SE aspect. 5400 ft.

    Photo: ONP Rangers

  • Loose Wet

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

    Expect the potential for natural wet loose avalanches as soon as the sun starts to poke through the clouds and heat up rocks, trees and cliffs. Once these start to shed, they will entrain snow on the slopes below. Rollerballs and moist snow surfaces also portend the problem. Reduce your exposure to steep slopes, especially those above you if the sun makes an appearance. You can always shift to shaded aspects which should stay cold.

    Example: wet loose avalanches once the sun comes out.

    Photo: Sam Luthy

Avalanche Discussion

Hurricane Ridge added 18" of snow since last Sunday. Around 10-12" of that likely arrived in the last 24 hours. A large rider-triggered avalanche in the 20th of June slide path (pictured in the wind slab problem) adds some questions to the mix. Was this just a wind slab within the recent storm snow, or did this run down to the 03/17 crust on this SE aspect? It would be worth investigating the bond to this crust on less shaded aspects? Although the storm relents by Saturday, there's enough recent dry snow that it adds some uncertainty to our forecast. While we expect wind-loaded slopes are the most likely trigger points, you could still find isolated areas of reactive storm snow. And there may be a crust lurking 1-3 ft down on some aspects that could be problematic. 

On Thursday. short-lived instabilities were developing within the storm snow. This produced cracking and even a small 4-6" natural avalanche at the edge of a tree well. The new snow fell down to 4000 ft Wednesday night, but warmed significantly even on shaded aspects below 4500 ft.

Multiple human-triggered avalanches occurred at Hurricane Ridge the weekend of March 15-16. Around March 17th, a crust on W-S-E aspects was a shallow amount of new snow. 

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