Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You can trigger slab avalanches in areas of recently wind drifted snow. Moderate to strong east winds on Thursday built fresh slabs - in some places on less commonly loaded west aspects. Work around steep slopes where you identify wind drifted snow by traveling on lower angle, more planar terrain.

Problemi valanghivi

  • Wind Slabs

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

    Strong winds and active loading were observed across the zone Thursday. Winds should taper by Friday morning but unstable slabs will remain in some areas.  Wind slabs may be easier to trigger where they formed over a crust on solar aspects. Danger from wind slab avalanches is lower in areas like Crystal which received notably less snow from the last storm.

    Cornices and other clues that show the usual direction of wind loading - normally from the south and west - will be less useful than normal. Freshly scoured ridgelines with smooth, fat, or pillowy-looking drifts on the slope below are the most obvious places where fresh wind slabs might lie in wait. Test slopes and hand shears will help gauge wind slab reactivity and depth and can help you identify areas where they are easier to trigger.

     

    Keep an eye out for wind-affected snow and signs of wind loading. These wind-textured surfaces indicate wind-loaded slopes nearby.

    Photo: Dallas Glass

Avalanche Discussion

Avalanche Fatality: Colchuck Pk, East Central Zone: Read the preliminary report here.

Loose snow avalanches are another consideration for Friday and the type of instability you are most likely to see. Light-density snow in sheltered areas should still sluff easily on steep and shady slopes. 

Warmer temperatures, light winds and full sun will trigger signs of instability like small rollerballs and even smaller avalanches. Keep an eye on steep terrain overhead as the day heats up and pull back if you see more activity than anticipated.

Strong winds and snow showers shifted to the east on Wednesday as temperatures dropped into the teens and single digits. White Pass reported east winds were transporting new snow onto west aspects Wednesday afternoon.  Strong winds were reported from both Crystal and White Pass on Thursday.

Avalanche activity should be limited to new snow and wind slabs above the recent rain crust/refreezing wet snow. Large avalanches breaking into deeper layers could occur with a big trigger like a cornice or a smaller avalanche.

Snow totals (and snow levels) from the latest storm varied widely across West South with several inches of water translating into 1’ or more of snow for areas like White Pass, St. Helens, and Paradise.  Areas shadowed from heavier snowfall - namely Crystal Mt and Chinook Pass - saw substantially less snow (and rain) over this period. 

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