Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Stormy weather will create dangerous avalanche conditions in many areas of the zone on Friday. Steer around slopes greater than 35 degrees if you find more than 8 inches of new snow or experience periods of heavier precipitation.

Problemi valanghivi

  • Storm Slabs

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

    With these warmer temperatures, the new snow could create an upside-down slab over the much colder and drier snow from last week. As a result, you could see avalanches failing at the base of the storm snow (4/5 interface). Use hand pits, small slopes, and up-track tests to see how the upper snowpack responds. If it cracks, fails in blocks, or shears off suddenly, then stay off of steep open slopes. 

    Expect potential avalanches to be larger at higher elevations and in locations that receive the most snow. Since precipitation should start to taper on Friday, these slabs could be easiest to trigger first thing in the morning.

    (3/11/2023)

    Cracks like this ares signs of unstable slabs of snow.

    Photo: Dallas Glass

  • Loose Wet

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

    We think most of the natural loose wet avalanches will have occurred Thursday afternoon/evening during the peak of the warm rainy weather. However, if you’re near or below the rain-snow line Friday, you could still trigger one of these slides. Wet mushy snow, new rollerballs, and small fresh piles of debris all serve as clues that loose wet exists in nearby terrain. Most of these avalanches should stay rather small but on a long continuous slope, they could entrain enough snow to grow large and deadly. Use caution on and under steep slopes, especially during periods of heavier rain.

    (1/14/2023)

    Example: You could see wet slides like this at lower elevations Friday. NW aspect ~4300'

    Photo: NPS Rainier Rangers

Avalanche Discussion

This storm continues to have a wide range of impacts across the West South zone. The southerly flow favors the volcanoes. Not surprisingly you’ll like to see the largest avalanches and greatest hazard near Mt St Helens and to a slightly lesser extent Mt Rainier and Mt Adams. Locations like Government Meadows and White Pass could receive substantially less precipitation, and result in a lower hazard in those areas.  

Observations were limited Thursday, but weather stations across the zone offered a pretty clear picture of how this warm wet storm was playing out. Snow levels seemed to hover near 5500 feet in most places. Sites near Mt St Helens recorded well over an inch of water, while White Pass only mustered about 0.1 inches. In general, most of the zone recorded 0.5-0.7 inches of precipitation. We expect similar trends to continue Thursday night and into Friday. 

Prior to this storm, about 1-2 feet of settled snow sat over the 3/31 crust. Recent avalanche activity was generally limited to small natural loose wet avalanches and a few intentionally triggered wind slabs. 

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