Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Wed
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In sintesi

On Tuesday, You could encounter various types of loose avalanches on steep slopes. More concerning is the potential for triggering a larger slab avalanche in wind-drifted snow below ridgelines or the base of cliffs. Watch for cracks shooting through deep snow drifts or heavy wet snow as signs to back off steep terrain. 

Problemi valanghivi

  • Wind Slabs

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

    Wind slabs are gaining strength, but you could still trigger one in isolated areas. Consider choosing more conservative terrain on slopes below corniced ridgelines, the base of cliffs, and confined rocky features. On northerly aspects, wind slabs rest over weak, faceted snow from the January Drought, so avalanches may be much larger and more dangerous.  Cracks shooting through stiff snow is a sign wind slabs are still unstable. 

    Wind slabs and fresh snow fell on inconsistent and variable surfaces, including slick crusts, wind-stiffened snow, and weak, faceted snow. The variability in both deeper weak layers and surfaces makes the distribution of triggering avalanches tricky to forecast. So, while you can make observations using test slopes and hand pits to observe how the new snow reacts, those results might not apply to nearby slopes. Make sure to make frequent assessments of stability in wind-affected terrain. 

    (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

  • Loose Wet

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

    There is some uncertainty in the cloud cover for Tuesday, but with mild temperatures and the chance for prolonged sun breaks, southern aspects could warm up quickly. So you could see rollerballs or small, wet loose avalanches at lower elevations. These avalanches may run naturally from trees and rocks shedding snow onto steep slopes below or you could trigger them on a steep slope in the sun.  If the snow starts to feel wet and heavy, move to shadier or lower-angle terrain. 

    On northerly aspects, dry loose avalanches are likely in steep terrain. Most of these will be small, but be aware of potential overhead hazards and make sure you don't sluff out your backcountry partners below.

    (12/12/2023)

    Examples of wet loose avalanches initiated from rocks shedding snow onto slopes below. 

    Photo: Matt Primomo

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    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 becoming less likely. But with the increasing temperatures, we're not quite ready to put this problem to bed. You can dig down and find the weak, sugary facets from the January Drought Layer 1-2ft below the snow surface. The distribution and reactivity of this problem remain elusive. But if you find this strong over weak layering, consider the consequences of a large avalanche. 

    (2/7/2025)

    A natural avalanche that likely ran on the 4-5th. The wide propagation suggests that it could have ran on the January Drought Layer. 

    Photo: Katie Warren

Avalanche Discussion

The Washington Pass area received 8-10 inches of low-density snow from the weekend storm. Temperatures increased slightly on Monday, with lower elevations bumping above freezing. Tuesday will bring additional warming and the chance for sun breaks before high clouds increase in the afternoon. 

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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