Bollettino valanghe

East Slopes South

Northwest Avalanche Center
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Pericolo valanghe

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

Your risk of triggering a very large slab should make you think twice about consequential terrain as incremental loading continues. Choose smaller features, lower angled slopes, and supported features to manage the risk. If temperatures rise above freezing in your area, wet loose avalanches could catch you on slopes steeper than 35 degrees.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    We think that a bit of cooling Tuesday night will help reduce the risk of human-triggered avalanches just slightly, but an additional 4-6" of snowfall during the day will stress existing weak layers.

    The risk of a surprising avalanche that breaks 2-4 ft deep remains on open slopes 30 degrees and steeper that don't have a firm, supportable crust near the snow surface. That likely includes most upper and middle-elevation slopes and possibly shadier lower-elevation slopes that managed to stay cold during Tuesday's warmup. These avalanches will be large enough to bury people and may propagate widely. WSW winds will create larger, thicker slabs that will be easier to trigger on wind-loaded slopes and may step down to the existing weak layers. However, you aren't completely safe on any aspect, including those sheltered from the wind. 

    A rider in the Manastash Ridge area remotely triggered one of these persistent slab avalanches on Sunday. This is good confirmation that the problem extends into the East South zone. Very large avalanches in the adjacent West South and avalanches to the north (East Central) also make it a good bet this problem also exists here. Weak facets exist on and within several crust layers buried deep in the snowpack. These avalanches could now be 2-4ft deep and potentially unsurvivable. 

    (1/20/2024)

    A rider remotely triggered this avalanche near Manastash Ridge on Sunday, January 21st. We suspect that it ran on the Solstice Crust and similar avalanches are wide spread in the more eastern areas of the Cascades. 

    Photo: Chris Ofsthun

  • Loose Wet

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

    Mild temperatures Monday and Tuesday impacted snow surfaces at lower and possibly middle elevations. With cooling forecast for Tuesday night, there should be a firm crust at middle elevations by Wednesday morning, but that crust may be very thin or non-existent at lower elevations. Wet snow you can sink into up to your ankle will help you identify the problem and it may overly very weak, dry snow; and if you find this snow surface condition stay off slopes steeper than 35 degrees. In some areas, new snow may transition to rain during the day. If this occurs, expect shallow wet loose avalanches that could pick up mass on a long, open slope or push you into a terrain trap.

    (12/7/2023)

    An example of a wet loose avalanche. 

    Photo: Willie Webster

Avalanche Discussion

We're expecting cooling to help firm up the snowpack a bit Tuesday night. Then, we're expecting 4-6" of snowfall during the day, adding stress to weak layers and forming shallow surface slabs you can trigger and that may step down to weak layers. We're also expecting a warming trend with snow levels rising during the day. The  degree of overnight cooling and the exact snow levels remain uncertain. With that in mind, you'll need to assess whether the forecast is in line with the weather trends you are experiencing. More warming than forecast, could create more dangerous conditions than we expect. On the other hand, more widespread surface crusts to start the day, could start to limit the distribution of the persistent slab problem. 

In addition to the avalanche on Manastash Ridge, multiple human-triggered avalanches have occurred near the Blewett Pass area over the past few days. These are failing on the Solstice Crust, and many have been remotely triggered from adjacent slopes. An NWAC forecaster at Crystal Mountain saw a suspiciously large avalanche in Morse Creek, very close to the border of East South. With uncertainty regarding the weather and evidence of large avalanche activity on 1/23 at Crystal Mountain and in the adjacent EC zone, build wider margins into your travel plans to account for this, and pay attention to warning signs such as collapsing, shooting cracks, or recent avalanches. 

If you get out, let us know what you see by submitting a public observation!

 

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