Bollettino valanghe

Olympics

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

With 3 ft of recent snow low-density snow, you can easily trigger loose avalanche avalanches large enough to bury you in a terrain trap or extreme terrain.  Stubborn wind slabs may be triggered on unsupported rollovers near exposed ridgelines.  Given limited observations, adopt an assessment mindset before moving onto larger open slopes or complex terrain. 

Problemi valanghivi

  • Wind Slabs

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

    Wind slabs are reaching the tail end of their lifespan and becoming stubborn to trigger. With all the recent snow, a wind slab would likely be large. We've received limited observations for the last few days of the storm cycle, with no direct observations above treeline. The lack of knowledge regarding the distribution of the problem and potential reactivity should remind us to take a step back and fully assess the storm snow before moving into more committing terrain near and above treeline. You'll need to find a safe location below to dig down to the most recent crust, noting any locations where firmer snow sits on top.  Low-density unconsolidated snow may overly these older slabs. After evaluation, avoid these wind-loaded slopes at upper elevations if you identify such a slab structure.

     

    (12/24/2021)

    Human triggered slab avalanche on Sunrise Face, just outside of the Hurricane Ridge ski area.  N/NE aspect. 

    Photo: NPS

  • Loose Dry

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

    It won't be hard to initiate a loose dry avalanche on steep slopes approaching 40 degrees at any elevation. If you're a strong rider, make a plan to limit your exposure to terrain traps such as cliffs, rocks, or gullies on the slopes below. If you're unsure, choose slopes less than 35 degrees.

     

     

Avalanche Discussion

Monday will be bitterly cold with temperatures not far from 0F. Make sure you are prepared for the unusually cold conditions and think through the consequences of any accident leading to extended exposure in backcountry terrain.

A 6-day storm cycle at Hurricane Ridge has delivered over 3' of fresh snow this week with a cooling trend, bringing the snow depth to 58" at Hurricane Ridge on Sunday. While Hurricane Ridge picked up 10.5" of snow since 12/24, down at 2100 ft on the access road, ONP rangers reported 14" of fresh snow from the upslope snowfall event. Thus, there's plenty of snow to bury you at any elevation if you get it moving.  While we don't currently have a storm slab problem in the forecast, cold temperatures may have preserved layering within the storm snow. You can use informal tests such, such as stomping a bit after you make a sharp turn in your uptrack to quickly assess this potential.

Soft wind slab avalanches were reported both Thursday and Friday in the Hurricane Ridge area.  On Thursday, NPS and NWAC observers found sensitive wind slabs up to 16" deep that were easy to trigger below ridgelines.  Small loose dry avalanches, or sluffs, released in steep terrain along the Hurricane ridge road as the snow continued to pile up.  The Dec 21 (solstice crust) can be found just over 2' down, with a thicker melt-freeze crust from Dec 19 several inches below it.  Observers identified weak snow grains (facets) below the 12/21 crust.  While snow pit tests did not indicate avalanches are likely to propagate on this layer,  remember we have a limited sample size for a large backcountry.  Observe, test, and consider your terrain choice before jumping onto big open slopes over the holiday weekend.  And please share your observations with us and your backcountry community, we love concise observations along with photos. 

Happy Holidays from the NWAC team and stay warm over the next week! 

2021-22 Forecast Schedule: Avalanche danger ratings will be issued for the Olympics every Friday through Sunday and during mid-week holidays. During the week when the Hurricane Ridge road is closed, forecast information will be updated daily to include expected conditions and relevant travel advice under the No Rating label.

Regioni coperte