Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Thu
Alta quota
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

This storm isn't a big snow producer for the East North. But it's just enough to maintain the possibility of triggering avalanches on wind-drifted slopes below ridgelines and confined chutes. If you find cracks shooting through wind-textured snow or observe recent avalanches, choose lower-angle routes.

Problemi valanghivi

  • Wind Slabs

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

    A bit of fresh snow and gusty ridgeline winds could build fresh wind slabs at mid and upper elevations. Consider choosing more conservative terrain on slopes below corniced ridgelines, the base of cliffs, and confined rocky features. You can use small test slopes or quick hand pits in lower-angle wind-affected terrain to observe how the snow reacts. Stiff layers that slide easily on softer snow mean triggering avalanches is more likely. On northerly aspects, wind slabs rest over weak, faceted snow from the January Drought, so avalanches may be much larger and more dangerous.  

    Older wind slabs and fresh snow formed over inconsistent and variable surfaces, including slick crusts, wind-stiffened snow, and weak, faceted snow. So, while you can make observations using test slopes and hand pits to observe how the new snow reacts, just be aware those results might not necessarily apply to nearby slopes.

    (1/31/2025)

    A natural wind slab from earlier this season at the base of cliffs, where stiffer snow settles. This is terrain where you could trigger a wind slab on Monday. 

    SS-N-R2-D1-I

    Photo: Katie Warren

  • Persistent Slabs

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

    This is a low-likelihood, high-consequence avalanche problem. You'd be unlucky to find just the right spot for triggering one of these avalanches, but the subsequent avalanche could take you for a nasty ride and/or fully bury you. With persistent slab problems, you may or may not observe signs of instability before triggering an avalanche. The safest travel choice is simply to avoid steep terrain on wind-loaded slopes below ridgelines or the base of cliffs on northerly aspects where this problem is most likely.

    There haven't been many new observations of instability on these weak, faceted layers, and triggering a large persistent slab is unlikely. With these tricky avalanches, signs of instability might not be apparent before triggering an avalanche. You can dig down and identify the weak, sugary snow layers 1-2ft below the recent snow and avoid slopes where you find this layering, likely on northerly aspects. If you choose to travel on steep slopes where this structure exists, consider the consequences and target more planar slopes without terrain traps.

    (2/6/2025)

    This large (D2) slab avalanche was likely triggered by cornice fall and we suspect it ran on the JDL weak layer. 

    Liberty Bowl, NNW, 7,200ft

    Photo: John Lucia

Avalanche Discussion

Even as this next storm enters our region, the models aren't in great agreement with how much precipitation we'll receive. But it doesn't look like the Washington Pass area will pick up more than a few inches of fresh snow. Along with that, winds might prove to be more gusty than steady and productive for wind slab formation. There is a chance the easterly component of the storm could bring more snow than anticipated, so it will be worth checking in on the weather in the morning to see how this storm plays out. 

The current snowpack is weak and faceted but also highly variable. The January Drought Layer consists of weak, faceted snow and was buried first by wind-drifted snow of varying depths. It wasn't until the early February storms that we saw avalanche activity on this layer. Most of those avalanches occurred in wind-loaded terrain on northerly aspects, failing on the January Drought Layer. In particular, many avalanches were right at the base of cliffs, where snow drifting down collects. A couple of isolated, small wind slabs failed on sun crusts on southern and western aspects. A single avalanche incident failed on a much older layer of faceted snow from mid-December. We don't expect this layer to be widespread or reactive, but it could be lingering in areas with a shallow snowpack in steep, rocky terrain. 

Lower elevations and eastern areas of the zone harbor a very weak, faceted snowpack because they stayed in the deep freeze below the inversion as upper elevations warmed in January. On Saturday, an NWAC Forecaster found a thick layer of very weak, faceted snow below last week's storm slab. With warmer temperatures, we could begin to see the overlaying snow form more of a cohesive slab, but that remains to be seen. 

You can help us gather more data by submitting an observation HERE or via the Avy App. 

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