Lawinenlagebericht

East Slopes North

Northwest Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

Steer around steep open slopes at upper elevations where winds have drifted fresh snow.  You're more likely to trigger a wind slab near and west of the Cascade crest.  Look for increasing avalanche danger Sunday night and Monday with an even stronger, wetter storm headed our way.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–1.5

    Steer around steep open slopes at high elevations where you find freshly drifted snow.  It's here you may trigger an avalanche in the new snow.  Watch for signs of instability like cracking and evidence of recent avalanches. In isolated areas, wind slabs may break from lower angled slopes below or break more widely than expected if they've built over recently buried surface hoar.  

    Example of the type of shallow new wind slabs you could trigger below ridgelines on Sunday. 

    Photo: Will Govus

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    2

    Unless far more snow falls than forecast, this likely won't be the storm that re-awakens the persistent slab in this zone.  That could change quickly Sunday night and Monday as an atmospheric river takes aim at the region.  While we haven't seen an avalanche on this layer in about 2 weeks, start to think about dialing back your terrain choices when conditions really begin to change.   

    However, on Sunday,  triggering a persistent slab avalanche remains unlikely.  You can find and test the weak layer in snowpack tests on shaded slopes near and above treeline.  While the depth varies, you can find the late January facet/crust interface somewhere between 2-3" below the snow surface. This layer is a combination of weak sugar-like facets sandwiched between two crusts in many areas. Sometimes you'll find weaker snow above the crust. The weak layers are deepest near and west of the Cascade crest and in wind deposited areas. 

    Red flags signaling that you may trigger a persistent slab avalanche include whumpfing, collapses, and snowpack tests that show sudden test results.  When in doubt, consider steering clear of shallow, rocky, or unsupported steep slopes.

    (2/12/2022)

    A natural D1.5 avalanche, occurred Feb 10 or 11th, likely on the late January persistent weak layer.

    Porcupine Pk, E, 7,400ft.

    Photo: Tino Villanueva

Avalanche Discussion

Observers on Friday found surface conditions to consist of a mix of weaker snow grains; patchy surface hoar and near surface facets on northerly aspects while widespread surface hoar had grown on southerly aspects. Look for these layers as new snow piles up over the next few days. They also found the 10-14" of last weekend's snow (totals near Washington Pass with much lower totals further east) settled and well bonded to the underlying crust.  Avalanche activity was minimal during the week. Professionals reported a few small wet loose avalanches during a sunny Friday with light winds.  Earlier in the workweek,  small but fast moving loose dry avalanches were reported in very steep terrain.  The very cold temperatures of the last few days will be a thing of the past as a pattern change takes hold starting Sunday afternoon and a relatively milder regime takes hold.  

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