Bollettino valanghe

Olympics

Northwest Avalanche Center
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Pericolo valanghe

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2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Slabs will remain reactive where you find denser warmer snow over lower-density colder layers. Wind drifting will enhance the problem. Steer or steep or unsupported slopes until these instabilities have time to fully settle out.

Problemi valanghivi

  • Storm Slabs

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

    By Sunday, we're 12-24 hours out from snow that fell with warming temperatures Friday night and Saturday. You're likely to find 1.5-2 ft of snow above the solstice crust. Much of the top 6-8" may have fallen "upside down" with denser over less dense layering. A few inches of lower-density snow may mask this slab as it falls on Sunday. Winds will exacerbate the existing storm slab layering, making the problem more acute in thicker deposits near ridgelines. Use a pole to probe for a subtle higher-density layer in the upper snowpack as you travel. Steer around steep or poorly supported features in the terrain and use test slopes to evaluate the slab character before engaging with larger slopes or upper-elevation terrain (where more uncertainty exists due to a lack of observations at these elevations).

    (12/28/2024)

    Intentionally triggered size 1.5 storm slab @ 5200 ft, NW aspect. Slab released on a poorly supported feature in the terrain.   

    Photo: Sam Siemens-Luthy

Avalanche Discussion

ONP rangers reported excellent riding and few signs of instability on Thursday and Friday without much of a slab, but by Saturday the 6" of new snow was warmer, denser, and had a slabbier character - particularly below 5000 ft. ONP Rangers were able to trigger two small avalanches on test slopes. In these slabs the upside down character of snow was exacerbated by winds further densifying the snow surfaces.The recent snow arrived with 10-15 mph ridgeline winds, so the focus of this wind redistribution should not extend particularly far downslope. Since the solstice crust was buried, Hurricane Ridge has picked up around 22" of snow and observers found this snow to be well bonded to the 1 cm thick Solstice Crust. 

Much of the wind during the Christmas-Boxing Day storm redistributed higher-density snow, forming gargoyles as winds shifted directions multiple times.  In many cases the winds redistributed some of this snow well downslope, depositing it into forests. We don't have any concerns below the Solstice Crust, but the 12/7 crust (also 1 cm thick) is easily identifiable above melt forms. Check out the snow profile in the gallery from 12/27.

Coverage is thin below 4400 ft, but Friday night's snowfall brought some warm snow down to 3800 ft. At these lower elevations, the shallow coverage limits the slab hazard, but consider the impact of even a small avalanche around terrain traps such as creeks, and gullies. Open creeks, downed logs, brush, and thin coverage make for slow going and many hazards are now barely submerged.

Regioni coperte