Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

An uptick in westerly winds may begin transporting snow on the higher peaks and exposed ridgelines. The real consequences lie in the potential to trigger much larger and wider persistent slabs at mid and upper elevations. Look for simpler, less steep, and more supported terrain while these dragons linger.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–2.5

    The chances of triggering a large persistent slab remain possible. Put a larger buffer of terrain between your group and large start zones or complex avalanche paths above 6,500ft. Choose smaller, well-supported slopes and stay well out from under larger features. Signs of instability can be inconsistent, creating a tricky problem that is essentially 'unmanageable'. You might not receive signs of instability before the whole slope fails. It could be the 2nd, 3rd, or 8th person on the slope that triggers it. A layer of surface hoar and facets were buried on 2/24, as was faceted snow over a strong crust from late January. You could find these two layers 1.5-3ft down and 2-4ft down respectively. These rest under a hefty snow load, and have been the culprit of numerous close calls in the zone. 

    A very large avalanche was triggered by skiers on 3/2 on Kangaroo Ridge. This broke very widely and ran almost the entire length of the path. 

    Pk 8183, WNW, 7,600ft

    (3/2/2024) Photo: Willie Webster

  • Wind Slabs

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

    Westerly winds should begin to pick up a little by Thursday morning and drift low density snow into thin slabs. Though shallow, these slabs could be fairly reactive as they'll often build over faceted surfaces. Look for signs of wind slab like observations of blowing snow, textured surfaces, and thicker or hollow sounding areas. Shooting cracks are signs of instability that you may encounter if you find a slab. Identify terrain and features within it where these are likely to exist. Although the consequences of one of these slabs may be minimal, any shallow slab could step down and trigger a much larger, wider avalanche on deeper weak layers. 

    Wind drifting snow near ridgelines.

    Photo: Matt Primomo

Avalanche Discussion

Thursday should be another beautiful, sunny day in the mountains. A bump in winds may begin transporting snow from higher peaks and ridgelines. The strengthening March sun may begin to have more of an affect on snow surfaces, especially those steep slopes that face SE-SW. Don't be surprised to see a few small loose wet slides on steep slopes in the sun. Continue to choose your terrain carefully while the persistent slab adjusts over time. 

Profile observations of buried weak layers have been variable over the past couple days, but many tests still receive sudden or propagating failures. Small loose dry and loose wet avalanches have been reported on steeper slopes the past couple of days. On Tuesday, a few small wind slabs were triggered by skiers on higher elevation slopes. Multiple close calls and numerous snowpack observations in the Highway 20 corridor point to a couple of buried weak layers (2/25 and 1/31) in the top 2-4 feet of the snowpack. On Saturday, an NWAC observer witnessed a group trigger a widely breaking, very large avalanche on Big Kangaroo. It ran almost the entire length of the avalanche path. In a sepereate event on the southeast sholder of Cutthroat Peak (6,400ft, SE) a party remotely triggered avalanches that propagated to either side of them 800-1000ft after leaving a profile site that they dug on the slope. Widespread very large natural avalanches continue to be observed throughout the area, and likely occurred Between the 28th and 1st.

Snowpack information is limited outside of the Highway 20 corridor and Harts Pass. Let us know what you find if you get out into the backcountry!

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