Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

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

Pay attention to shifting and locally strong winds Monday. With plenty of powder available for transport, unstable slabs of wind drifted new snow will quickly build anywhere the wind gets a chance. Assume a higher level of danger including and south of the Mt. Loop as that area received significant new snow in the last 24 hours. Look out for wet avalanches during periods of sun or warming.

Problemi valanghivi

  • Wind Slabs

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

    Avalanches in freshly wind drifted snow will pose the greatest danger on Monday. Though forecasted wind speeds are not quite high enough for widespread and consistent transport,  locally stronger winds could result in reactive new slabs. This is even more so the case traveling farther east in the zone or climbing into alpine terrain. Natural avalanches are possible during periods of intense transport. Don’t linger under steep slopes that are actively wind loading.

    Blowing snow will be the best indicator of active wind loading.  Also, note the pattern of wind scoured versus loaded slopes to help identify where wind slabs might lurk. Track the change in snow depth as you move in and out of wind affected terrain and look for stiff slabs overlying weaker snow below. Hand pits and test slopes can help you gauge the bond of new wind slab layers. The best policy might be just to steer around steep slopes with signs of active or recent wind loading

    Expect greater danger and even a few natural avalanches in areas with stronger wind and extensive wind transport.

  • Storm Slabs

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

    If you are traveling in the southern reaches of West Central expect to see deep new snow out of wind affected terrain at lower and mid-elevations. Though the new snow layers should bond quickly, be patient approaching steep slopes and investigate how well the new snow is bonded before committing to avalanche terrain. Slabs of new snow could also become more reactive with warming as a denser slab forms over colder and weaker snow below.

    Wet loose avalanches are also possible as cold snow warms and becomes wet on sun exposed slopes. Move off and away from terrain where you see rollerballs or small wet loose avalanches during sunbreaks or with rising temperatures. Wet avalanches pack much more of a punch than their dry loose cousins and you just don't want to be in the way no matter how small they look. Even a small avalanche could carry you over a cliff or into a terrain trap.

Avalanche Discussion

West Central currently sports a wide range of conditions with the current weather pattern that might be better reflected in the forecasts of each adjacent zone near where you travel on Monday.

In West North, heavy snowfall Saturday gave way to sunny skies, excellent snow conditions, and moderate avalanche danger. Extensive travel in steep terrain produced numerous loose snow avalanches that were a size above what is normally seen after a storm. Wet loose were also reported with periods of solar radiation and most sun exposed slopes produced natural avalanches up to D1.5. No wind slab avalanches were observed by those traveling in alpine terrain. They did report identifying and avoiding the steepest wind loaded features. Sun and a midday rise in temperature affected the snow surface well above treeline and on all aspects at lower elevations. 

Quite the opposite of this was heavy snowfall on Sunday from Hwy 2 southward to Snoqualmie Pass.  With 2' of new snow, a natural avalanche cycle occurred at all elevations with numerous storm and wind slab avalanches reported. Stevens Pass lies a bit in the middle with snowfall spread out across both Saturday and Sunday with 12" in the last 36 hours and 4" today. Check the forecasts for Steven Pass or Snoqualmie Pass if you are traveling adjacent to those zones.

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