Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

After a cool night, springtime temperatures should again impact much of the zone on Thursday. As the day wears on, expect firm surfaces to thaw and wet avalanche likelihood to increase. If you are sinking in the snow past your ankle or see fresh rollerballs and pinwheels, avoid slopes over 35 degrees.

Problemi valanghivi

  • Loose Wet

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

    Wet Loose avalanches could occur on steep slopes over 35 degrees wherever the snow surface is heavy and wet on Thursday. This could be more likely as the day wears on and warm temperatures destabilize the snow surface. Wet Loose avalanches often start at a point and fan out as they descend downhill, entraining additional snow or even triggering slabs. Visual clues such as fresh rollerballs and pinwheels are precursors to wet avalanches and can help you know that slopes may be reaching their tipping point. You can also take a moment to step into the snow and see if you are plunging in past your ankle to let you know that the snow is reaching the threshold for producing these slides. If you find that these conditions have been met, avoid open slopes over 35 degrees.

    (3/23/2022) Wet loose slide debris, roller balls, and rain runneling around Edith Creek Basin. Everything points to wet. Photo: NPS Rainier Rangers

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–2.5

    Our last confirmed avalanche on the 3/8 facets was on Friday, March 18. While this layer has appeared to go to sleep recently, it may not be completely put to bed. On Wednesday, a very large natural avalanche occurred near Mt. Baker in the West North zone on this same layer. Although the snowpack between our zones has diverged in recent days, this very large avalanche should be a reminder that persistent slabs can awaken suddenly and produce erratic avalanches. Dynamic springtime weather only increases uncertainty around this layer and recent observations indicate that the weak snowpack structure is still in place. Build in a wide margin for error when traveling near commonly shady slopes at mid to upper elevations. Just because a slope has tracks on it or you dug a single hole in the ground without impressive test results doesn't mean that terrain is safe. 

    (3/18/2022)

    A skier triggered avalanche on Mazama Ridge near Paradise, Mt Rainier NP. 16" deep. W aspect, 5600ft. This avalanche faild on the 3/8 facets over the Early March Crust. HS-ASu-D2-R3-O

    Photo: Public Observation

Avalanche Discussion

Wednesday night should deliver cool temperatures to much of the zone for the first time in a few days, helping to stabilize the snowpack from the top down. The exception may be further south, where warmer temperatures are expected. If you find a firm surface in the morning, then the freezing process likely occurred and avalanche activity could be minimal. This stability could be short-lived as rising temperatures throughout the day will only increase the likelihood of wet avalanches and cornice collapses. In some locations, a few inches of fresh snow could even fall on Wednesday night during the cold frontal passage. If you find fresh snow in the morning, expect it to get wet and sticky and possibly produce small wet avalanches in the afternoon.

The upper snowpack around the zone is generally saturated due to rain and warm springtime weather in recent days. NWAC weather stations have shown impressive settlement rates since our most recent storm over the weekend, showing that the snowpack should be gaining strength. On Wednesday, NPS rangers at Mount Rainier reported soggy conditions and natural Wet Loose avalanches on multiple aspects. Similar conditions and warm temperatures were noticed in other parts of the zone and could persist if we get a poor refreeze Wednesday night. While you should focus most of your attention on the surface snow, don’t ignore the weaker snow just above the Early March Crust. This layer can be found around 3 feet below the surface and could be most reactive on shady slopes at mid to upper elevations.

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