Bollettino valanghe

West Slopes South

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
Open full map
Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Multiple feet of snow combined with strong wind has resulted in dangerous avalanche conditions within the West South zone. Be on the lookout for Wind Slabs near ridgelines or on convex slopes where triggering an avalanche is more likely - they may be hidden under some fresh snow. The southern volcanoes and White Pass have received the bulk of the recent storm cycle and could have larger or more reactive slabs. 

Problemi valanghivi

  • Wind Slabs

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

    The size and distribution of Wind Slabs should vary around the zone, but we believe that wind-loaded terrain is the most likely location for you to trigger a slab on Saturday. They may be hidden under recently fallen snow, so you’ll need to feel for changes in the upper snowpack as you travel to help identify wind-loaded areas. If you encounter stiffer snow, that could feel hollow, you know you’ve found the spots we’re concerned about. Near ridgelines, you still may be able to use visual clues such as newly formed cornices to give you an indication of where some of these slabs may be lurking. Unfortunately, the wind direction has flip-flopped in the last 24 hours meaning you now could find slabs on a variety of aspects. So key into terrain features where they’re more likely such as near ridgelines, on convex rollovers, or rocky terrain such as confined gullies and the base of cliffs.

    The recent storm path has been favoring the southern half of the zone so you could see slabs outside of wind-effected areas. Look for shooting cracks or blocks of snow failing easily on test slopes or in hand pits as an indication to start avoiding all steep slopes over 35 degrees whether they are wind-loaded or not.

    (3/11/2023)

    A naturally occurring slab avalanche at the base of a cliff band near Crystal Mountain. Avalanche professionals suspect this slide may have stepped down to a deeper layer.

    Photo: Joe Hoch

  • Loose Wet

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

    It’s getting to be that time of the year. Anytime the sun comes out and there is new snowfall, you should expect to see Wet Loose activity on steep sun-exposed slopes. The potential for extended sun breaks on Saturday is enough for us to list this as an official problem for the day. These avalanches often start at a point and fan out as they move downhill, sometimes growing large or triggering slabs as they descend. If you’re on a slope that sees direct sunshine and you notice snow shedding from trees and rocks or see new rollerballs/pinwheels, then it’s time to start considering heading for more shaded aspects so you don’t get tripped up by one of these slides.

    (2/19/2023)

    Example: If the sun makes an extended appearance, steep sunny slopes could produce piles of new rollerballs and a few Wet Loose avalanches.

    Photo: Dallas Glass

Avalanche Discussion

It’s been a stormy week for the West South zone! The southern volcanoes and White Pass have received 3.5 feet of snow, while Paradise is close behind with roughly 3, and Crystal has received approximately 2. Although snow totals vary widely from north to south and the hazard level may vary slightly, the overall message remains roughly the same. There’s been a lot of recent snow and you could encounter avalanches on steep slopes over 35 degrees. The snow isn’t done quite yet, either. We should squeeze out a few more inches before Saturday dawns. 

On Friday, scientists that work on Mount St. Helens reported that their seismic equipment picked up multiple large to potentially very large avalanches occurring on the mountain during the height of the storm. Forest Service employees also relayed that so much recent snow has fallen that road teams are having a difficult time keeping up with the removal process. At White Pass, avalanche professionals found deep unconsolidated snow showing plenty of signs of wind effect in exposed areas, even below treeline. 

Leading up to this stormy period, the snowpack around the West South was believed to be generally stable and right-side-up. We are anticipating all avalanche activity to be confined to the multiple feet of new snow that has fallen in the past week. With storm totals this deep, it is important to keep your partner in sight and don’t let them fall in an area where they could have a difficult time getting up. You can read up on Deep Snow Safety here.

Regioni coperte