Bollettino valanghe

Stevens Pass

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Steady snowfall and ridgetop winds should create fresh wind slab danger near and above treeline. Slabs could be fairly reactive, especially during periods of increased snowfall rates. Make observations as the day progresses- if you find more than 12" of new snow, expect more dangerous conditions and adjust your travels accordingly.

Problemi valanghivi

  • Wind Slabs

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

    Westerly winds will drift the slowly accumulating new snow into soft and shallow slabs. Old snow surfaces are a mixed bag of crusts and facets, and it may not bond well. Look for signs of drifting as you gain elevation, and check test slopes for cracking. Steer around steep slopes that are freshly loading, or if you find signs of instability. With potential for convergence zone enhancement, snowfall rates may become heavier at times on Sunday. Small loose dry avalanches may begin to run once enough new snow stacks up.

    If snowfall rates are sustained and heavy, or you find that over a foot has already fallen, then conditions may become more dangerous than anticipated. Be ready to re-evaluate and make travel decisions accordingly, and as the day progresses.

    Example small wind slab

    Photo: Ryan Minton

Avalanche Discussion

A change in the weather pattern is here, and we expect a slow increase in avalanche danger along with it. The very cold temperatures will help to squeeze out more snow than is typical for the amount of precipitation in the forecast. Additionally, chances appear good for the pass to get hit by a convergence zone during the day on Sunday. Even still, snowfall amounts somewhere in the 6-12" range through the end of the day appear likely. The snow will be falling on a mixed bag of surfaces. These range from soft 'recycled pow' with facets and surface hoar on sheltered, northerly aspects to various degrees of crusts on southeast to southwest slopes. 

An observation this past week showed a large glide crack opening on a southeast-facing slope of Jove Peak. Stay off of and well out from under slopes with glide cracks. Glide avalanches are difficult to predict and they can release with little warning. There are isolated rock slabs capable of producing these avalanches in the Stevens Pass zone.

Layers of weak snow and crusts were buried by a small storm on December 8th  (surface hoar) and a series of storms in late November (basal facets). These layers are now down about a foot and near the ground, respectively and have been gaining strength. These older layers generally haven't been a problem for avalanches in this zone as much as others throughout the forecast region, though it's something to consider, especially in any heavily wind-loaded areas and during/shortly after a big snowfall event.

Regioni coperte