Lawinenlagebericht

East Slopes North

Northwest Avalanche Center
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Lawinengefahr

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

You can trigger avalanches where the wind has drifted recent snow at middle and upper elevations. Steer around thick pillows and drifts on slopes steeper than 35 degrees. Continue to avoid very large, unsupported terrain features and complex terrain until we can rule out the slight chance of triggering large avalanches on deeply buried weak layers. 

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Cracks shooting through the snow are a "red flag" warning sign of this type of avalanche. You can also look for deeper, drifted areas of snow. You can use a pole or probe to feel the stiffer snow and compare the deeper drifts to wind-sheltered areas. Steer around slopes steeper than 35 degrees where you find these snowpack characteristics. Be aware of cornices and make sure not to travel on them or linger under them. In the past 2 weeks, there have been a number of avalanches triggered by cornice falls.

    From January 31-February 1st, 6-8" of dry snow accumulated above 5,800ft, and southwest winds formed stiff slabs and drifts. On Friday, observers intentionally triggered a small wind slab avalanche on a north aspect at middle elevations.

    (1/26/2024)

    Wind-sculpted features at upper elevations in the Blue Lake basin.

    Photo: Will Govus

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    2–2.5

    This is a low-likelihood, high-consequence problem. Time, space, and careful snowpack assessment are your best approaches until we can further rule it out. If you managed to trigger an older weak layer, an avalanche could break very deep and widely across terrain features. Continue to put a large terrain buffer between your group and large, unsupported terrain features and start zones. 

    There are two persistent weak layers that could still be a problem: small facets buried on or around January 8th in the top 1/2 of the snowpack and a series of crusts and large weak grains from December in the lower 1/3rd of the snowpack.  You can use snowpack tests to identify and assess these weak layers. The early January facets have been found in the Hairpin Valley, the Blue Lake area, and Varden Creek. Extensive snow profiles near Harts Pass in late January did not detect the weak layer there. 

    (1/30/2024)

    Multiple crowns of natural avalanches, including some that may have run on deeper weak layers above the Hairpin Valley at Washington Pass. These likely ran between Jan 27-29th.

Avalanche Discussion

Temperatures have cooled after the area experienced a prolonged period of warming and wet or moist precipitation. Below 5,800ft, most of the 1.75" of water equivalent fell as rain. Above that elevation, you can find up to 8" of recent snow resting on a crust or moist snow. As surface crusts gain strength with ongoing freezes, they may be enough to keep travelers from being able to trigger avalanches on deeper weak layers. On Friday, observers reported that low elevations saw extensive rain and looked "beat up." We anticipate that many layers at low elevations have transformed into melt forms, strengthening the snowpack. On a northeast aspect at 6,800ft in Varden Creek, observers found the recent storm snow resting on 8" of older moist snow. Below that, the snowpack was dry, including the December crust/facet layers. 

On January 30th, observers reported recent wet avalanches near Washington Pass (photos below), underscoring how active and prolonged this period of elevated danger has been. On the 28th, warm temperatures and rain resulted in natural slab and loose wet avalanches from Harts Pass. On the 27th, prior to the rain, observers on Kangaroo Ridge reported a large collapse on the January 8th facets and audible natural avalanches in nearby terrain. On that day, observers also remotely triggered a very large persistent slab avalanche on an east aspect at 6,000ft in Leap Creek. 

On the 24th, NWAC forecasters traveled near Blue Lake. At a profile site (NW, 6,650ft), they found propagating test results on the January 8th facets ↓65cm and sudden collapse failures on old facets and crusts from December. The January 8th facets were also a weak layer, ~2 feet below the surface, in an avalanche on Poster Peak.  If you're in the mountains, please let us know what you find.

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