Bollettino valanghe

Stevens Pass

Northwest Avalanche Center
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Pericolo valanghe

Thu
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

A relative lull in the weather Wednesday should allow for avalanche danger to decrease slightly. However, you may still trigger avalanches large enough to bury and kill you, especially at mid and upper elevations. Be particularly leery of areas of wind drifted snow that may provide the slab needed for avalanches to fail on very weak persistent snow grains.

Problemi valanghivi

  • Persistent Slabs

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

    Plenty of evidence supports the existence of weak sugary facets and occasionally buried surface hoar in the upper snowpack at Steven Pass. While we currently do not have any confirmed avalanches on this layer, that could change at any moment. You may find weak facets (1-1.5mm) and/or surface hoar about 4”/10cm above the recent stout crust, particularly at mid-elevations. You are most likely to trigger a persistent avalanche where the wind drifted snow formed a slightly firmer and thicker slab over these weak grains. Use visual clues such as wind drifts, cornices, and textured snow surfaces to highlight slopes you want to avoid. Persistent slab avalanches can be tricky and fool us by breaking in surprising ways such as on lower angled slopes, triggering remotely, or propagating widely. If you travel near or above treeline, give this challenging avalanche problem a wide berth.

    You can find thin stripes of facets and possibly buried surface hoar about 10cm/4" above a prominent crust.

  • Storm Slabs

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

    A series of recent storms created several potential weak layers within the upper snowpack. On Tuesday, NWAC forecasters found a natural storm slab avalanche failed on one such layer. While a brief lull in the weather Wednesday should allow these weaknesses time to gain strength, you may still trigger avalanches on specific features. Steer around convex rollovers, steep rocky slopes, wind drifts, and other common trigger points. Use small low consequence terrain to make observations. Up-track tests, small slope cuts, and simple hand pits can help you feel the storm slab and see how it fails under your weight.

    (12/15/2020) This natural storm slab occurred at Lanham Creek near Stevens Pass. It failed on a change in snow crystal type within the storm snow. NE aspect 5200' N-SS-D1-I

Avalanche Discussion

While none of the recent storms have been particularly impactful, they continue to stack up snow inch by inch. At this point, 10-16” (25-40cm) of recent snow rests above a very stout and prominent crust (12/09). One has to wonder when or if we will reach the tipping point with this new snow and see a more widespread avalanche cycle. Given the marginal additional snow input on Wednesday, we don’t expect this to be the day, but time will tell. 

At lower elevations, a thin snowpack and early season conditions continue to make travel difficult. Expect open creeks, areas of thin coverage, and shallowly buried obstacles. 

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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