Bollettino valanghe

East Slopes South

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

There is a lot of new snow, and an upslope easterly storm event may bring additional snow tomorrow. The most likely places to trigger an avalanche will be at upper elevations in wind drifted snow. So avoid steep slopes below ridges and steep convex rolls where you find "fat" looking drifts of snow.

Problemi valanghivi

  • Wind Slabs

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

    You can still expect to find reactive wind slabs on steep wind-loaded slopes and terrain features. The most likely places to trigger wind slabs will be steep slopes below ridges, steep convex rolls, and the base of cliffs. You will likely need to steer around these wind slabs in steep open terrain at lower elevations, but avoiding these wind slabs in alpine terrain may still be challenging. Feel for stiff over soft snow layering and use inconsequential test slopes to identify and avoid areas of unstable wind-drifted snow. Areas sheltered from the wind or low-angle slopes will be the best option to reduce to likelihood of triggering an avalanche. There has been significant snow and winds over the last 24hrs, and we are not entirely out of the stormy period yet. Older wind slabs may be trending towards more stubborn to trigger, but as the storm moves into the East South, new wind slabs may form quickly. Winds are forecasted to shift easterly, and fresh, shallow wind slabs may form on previously wind-scoured slopes. Pay close attention to wind direction and blowing snow to identify locations where snow drifts into shallow slabs.

    (2/28/2023)

    These pillow like drifts below ridges are prime locations to trigger a wind slab. 

    Photo: Katie Warren

  • Loose Dry

    • 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, you could trigger fast-moving dry loose avalanches in very steep terrain. 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

New snow accumulated on various surfaces, including slick crusts on southerly slopes and weak snow on northerly aspects. We are still in a stormy weather pattern and have limited information on how the new snow bonds to underlying surfaces, especially at upper elevations. As we start to step out from storm cycles, it's always a good idea to enter new terrain slowly and make observations as you travel. 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 mini avalanches. 

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.

I traveled into the Ahtanum Meadows area on Tuesday. Generally, I found 7-12 inches of new snow and excellent riding conditions. Snowpack test yielded unremarkable results. However, I did observe some weak snow below the Valentine's Crust, about 20 inches below the snow surface. You can check out my 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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