Bollettino valanghe

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Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
2 · Moderato
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 5 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Wind slabs may lurk on the lee sides of ridgelines as you move higher in the terrain. This problem will be more significant if winds increase and actively form slabs on the snow surface. Steer around steep slopes with active wind loading or recent lens-shaped deposits.

Problemi valanghivi

  • Wind Slabs

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

    Although wind slabs were very localized at middle elevations near Hurricane Ridge on Saturday, they are more likely to exist in more exposed terrain at higher elevations. This is also increasing WSW winds are likely to redistribute fresh and recent snow into denser drifts. Use small test slopes to evaluate wind stiffened layers before engaging with more complex terrain. Steer around areas of textured snow, lens-shaped pillows, and slopes below fresh, sharp wind lips if they overlap steep terrain. Remember that conditions could diverge quickly once you ascend above the 3/11 crust, which is likely to peter out around 5500-6000 ft. 

    Example: Wind textured slopes like this are a great indicator of possible wind slabs. 

    Photo: Sam Siemens-Luthy

Avalanche Discussion

We're expecting cloudy skies and surface crusts to limit wet loose activity on Sunday morning. An incoming storm will bring several inches of new snow and increasing light to moderate ridgeline winds Sunday afternoon, increasing the avalanche danger as the day progresses.

On Saturday, ONP Rangers reported several natural and human triggered D1 wet loose avalanches as strong March sunshine impacted and destabilized snow on W-S-E aspects despite temperatures topping out in the low 20s at Hurricane Ridge. Early in the day, observers mostly reported 12" of unconsolidated snow above the 3/11 crust which has thickened to 3" and remains knife hard. Observers noted surficial dry loose "sluffs" noted in steep terrain. 

With cool temperatures remaining in the forecast, a dry loose avalanche could still take you for a short ride on a slope approaching 40 degrees. On sun-exposed aspects you you are likely to find a thin surface crust and more consolidated upper snowpack by Sunday.

 ONP Rangers have been tracking a layer of weaker wet snow grains below the 3/11 crust. The crust is sufficiently thick to be a new ground at middle and lower elevations of the Hurricane Ridge area, but if you find it to be thinner and breakable in your terrain, take a look underneath the crust before engaging with steep slopes. The interface has been failing above a layer of low-density wet snow underneath beneath the crust. The rangers noted settlement at times while traveling on Thursday and one observer out toward Hurricane Hill heard an audible "whumph" on Friday.

The recent storm largely wrapped up on Friday with around 8-10" of new snow and it feels like winter once again! Coverage has drastically improved at middle elevations with Hurricane Ridge reporting 48" of snow depth and Maggies snow stake reporting 60". Even lower elevations now have some snow. Coverage remains poor in the trees, on windward aspects, and near ridges. Travel cautiously as rocks or barely submerged obstacles may exist just beneath the snow furface.

Regioni coperte