Bollettino valanghe

East Slopes South

Northwest Avalanche Center
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Pericolo valanghe

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

East winds have drifted snow onto atypical aspects with upper elevations holding the greatest risk for human-triggered avalanches. Continue to avoid bulging drifts below poorly supported slopes near ridgelines. Low-density snow keeps piling up in the East South zone with an unusual threat for snow immersion and suffocation in some areas: ride with a partner and keep them in sight. 

Problemi valanghivi

  • Wind Slabs

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

    Wind slab danger should gradually decrease as the winds and snowfall ease. However, it may not be simple to identify slabs in their typical locations. Winds continue to change directions, creating slabs on a variety of aspects, but we expect the E winds have moved the most snow. Fresh and more reactive slabs may be identified by subtle cornices with pillow-like drifts below them, but you may have to look carefully.  The most likely places to trigger wind slabs will be steep slopes below ridges, convex rolls, and the base of cliffs. You will likely need to steer around these wind slabs in steep open terrain near treeline, and the potential remains more elevated danger in heavily wind-exposed terrain above treeline. Feel for stiff over soft snow layering and use inconsequential test slopes to identify and avoid areas of unstable wind-drifted snow. Navigate away from lee slopes steeper than 35 degrees, instead choosing sheltered slopes and lower-angle terrain will offer high quality and safer riding conditions.

    Example: Wind loading in both directions.

    Photo: Sam Siemens-Luthy

  • Loose Wet

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

    With significant low-density snow accumulating over the last few days, loose avalanches may release in steep terrain. These could be wet or dry on sun-affected aspects with dry loose avalanches remaining easy to trigger and fast-moving on steep shaded slopes. These avalanches often start directly below your feet or as snow falls from trees and cliffs onto the slopes below. While they may tend to be more predictable than slab avalanches, avoid getting caught off guard in steep, consequential terrain where you could be carried over cliffs or buried deeply in gullies. 

    (2/22/2023)

    An example of small dry loose sloughs 

    Photo: Katie Warren

Avalanche Discussion

As the snow keeps piling up, keep SIS safety in mind: keep your partners in close sight and give tree-wells a wider buffer than normal.

Another 1-5" of snow fell around the ES zone in the last 24 hours. Some of the recent snow has accumulated over slick crusts on southerly slopes and weak snow on northerly aspects. We are still in a stormy weather pattern and have limited information regarding bonding and layering of the upper snowpack, especially at upper elevations. Sunday may feature some better visibility and it's a good time to move into the terrain with caution and a mindset of evaluation. You can use inconsequential test slopes and quick hand pits to observe how the recent snow reacts. Avoid steep terrain if you find the new snow sliding easily or test slopes producing clean shears.

A generally strong snowpack exists throughout the East South, and the recent storms have been improving winter recreation opportunities significantly. However, the recent snow has piled up on various crusts. While we have not seen any avalanche activity on deeper, older snow layers, we are tracking these interfaces with the additional loading events.

Katie Warren traveled to the Ahtanum Meadows area on Tuesday. They found 7-12 inches of new snow and excellent riding conditions. Snowpack test yielded unremarkable results. However, there was some weak snow below the Valentine's Crust, now about 2 ft below the snow surface. You can check out the observation here for more details. Before the storm cycle on the 25th, Joe Dellaporta traveled into the American Ridge area near Bumping Lake and observed slick surfaces at lower elevations, dry faceting snow at upper elevations in the shade, and a thin sun crust on slopes with a southern tilt (observation).  

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