Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

Winds drifted the recent snow into stiff slabs where you can easily trigger avalanches. Avoid steep slopes where drifted snow tends to collect, such as below corniced ridges, the base of cliffs, and alpine terrain features. As temperatures warm and the sky clears in the afternoon, wet avalanches may also run at lower elevations.

Problemi valanghivi

  • Loose Wet

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

    Temperatures will be a notch warmer on Saturday, and there is a good chance of some afternoon sun breaks. With this combination, you may see wet avalanches as the fresh snow warms up and becomes heavy and saturated. These avalanches tend to start with trees or cliffs shedding snow onto steep slopes, but you can also trigger these avalanches while skiing. Pay attention to overhead hazards and avoid getting caught in your sluff in steep consequential terrain. Wet loose avalanches may be possible on all aspects at lower elevations, but you're most likely to see these avalanches run on sunny slopes at upper elevations. Move to shady terrain or lower-angle slopes if the snow becomes heavy and wet or you start to see rollerballs on steep slopes.

    (3/10/2023)

    Wet loose avalanches like this one will become more likely with daytime warming on Saturday. 

    Photo: Matt Primomo

  • Wind Slabs

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

    Easterly winds were light during the bulk of the snowfall on Thursday and Friday. However, later in the afternoon, winds shifted westerly and quickly drifted the new snow into wind slabs on lee aspects. These wind slabs are likely to still be reactive on Saturday, so steering around steep wind-loaded terrain will be key to avoid trigging an avalanche. Expect wind slabs to be larger and easier to trigger as you ascend elevation. Use visual clues such as textured surfaces, deep pillowlike drifts, or feel for stiff over soft snow layering to identify likely wind slab locations. Wind slabs may be larger and easier to trigger than storm slabs, so avoid steep slopes and potential trigger spots such as the base of cliffs, convex rolls, and slopes below corniced ridges. Wind slabs should be your primary concern, but you may also find some isolated steep slopes where you could trigger a lingering storm slab. Make observations as you travel using small test slopes and quick hand pits to assess how the new snow reacts. Snow that slides easily in a cohesive block indicates that triggering an avalanche is possible.

    (12/30/2022)

    Example of long shooting cracks in a fresh wind slab. These long cracks are bullseye information of unstable snow.

    Photo: Rob Pollard

Avalanche Discussion

Thursday brought 8-10 inches of new snow to the Wenatchee mountains. Other locations throughout the zone received less snow overnight, but a continued trickle-in weather pattern keeps the snow piling up. If you find deep, dry new snow, then you'll likely be able to initiate small sluffs that run on steep slopes. You'll want to exercise caution near terrain traps like above cliff bands or tight gullies where a fast-running dry loose avalanche could knock you off your feet in the wrong place. 

Recent observations indicated the recent snow is low-density snow that lacks slab structure. Observers on Blewett Pass and Mission ridge reported mostly unconsolidated new snow with some isolated pockets of wind slabs. As the day progressed, westerly winds picked up, and wind slabs formed on lee aspects near and above treeline. New snow primarily showed a favorable bond to the underlying surfaces. However, new snow would slide more readily on a recent sun crust in some isolated areas on southern slopes. An excellent practice is continually evaluating the new/old snow interface as you change aspects and gain elevation. 

The recent soft snow rests over a couple of intermittent sun crusts and a pair of rain crusts from Valentine's Day, which can be found 1-3ft deep. These often present as a crust/facet/crust sandwich, with weaker snow beneath the upper crust. Observations indicate wide variability in the structure and depth of this layer throughout the zone. There are isolated observations with signs of instabilities on this layer in the Icicle drainage and the eastern Highway 2 Corridor. On Monday, observers near the Swath on the western edge of the zone reported small collapses on this layer on a north aspect between 5,600ft and 5,800ft. We don't currently anticipate avalanches on this layer but are monitoring it with additional loading events. 

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