Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

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

The Easter Bunny should bring a bit of a break in the stormy weather to the West South on Sunday. You could experience either dry or wet avalanches based on the time of day or a slope's exposure to sunshine. Watch how the weather is unfolding and changing the snow throughout the day as an indication of the type of avalanche problem you need to manage.

Problemi valanghivi

  • Wind Slabs

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

    Earlier in the day before the snow gets the opportunity to heat up, you could encounter some freshly built Wind Slabs. Snow showers on Saturday afternoon are expected to continue into the evening hours and be accompanied by moderate winds. This input could be just enough to produce some new unstable pockets near ridgelines or confined rocky chutes. The past week has been full of windy and snowy days, and lingering slabs from this period could also be found in isolated locations. On Sunday, actively blowing snow, fresh drifts, and some isolated cracking in wind-drifted snow were reported near White Pass. If you notice similar conditions on Sunday, fresh pillow-like drifts, textured surfaces, or inconsistent snow depths as you travel, be on the lookout for nearby wind-loaded terrain to avoid.

    (4/16/2022)

    Fresh drifts and pillow-like piles of snow are good indicators that the wind has been moving the snow around and Wind Slabs could exist in nearby terrain.

    Photo: Dallas Glass

  • Loose Wet

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

    Sunday should be the warmest day we’ve had in the last two weeks and sunshine could combine with the warmer temperatures to weaken the snow surface. If it's sunny out and you notice that the snow is starting to get wet and sticky or see it shedding from trees and rocks, then it's time to start thinking about Wet Loose avalanches. The window for these avalanches could be small, but if they occur, they will be more likely on steep slopes that see direct sunshine. This is April, however, so there’s a chance you could see them on more northerly aspects in some locations or they could linger after the sun has disappeared behind the clouds. Wet Loose avalanches often start at a point before fanning out and entraining snow as they descend downhill. Precursors such as rollerballs and pinwheels can let you know that the snowpack is reaching the threshold for producing these slides and you should head for shadier slopes.

    (4/16/2022)

    Rollerballs like these ones found in the neighboring Snoqualmie Pass zone are a good indication of potential wet avalanche activity.

    Photo: Andy Harrington

Avalanche Discussion

We haven’t had a whole lot of sunshine in the West South since a cold and snowy pattern began on 4/8. That may change on Sunday as a short-lived window of nicer weather should deliver sunshine and warmer temperatures than we have seen in recent weeks, at least for part of the day. Before that happens, we could squeeze out a few more inches of snow on Saturday night as we wrap up our cold and snowy pattern. Increasing clouds ahead of the next storm system should reach the zone sometime around midday on Sunday as it travels from south to north. 

These transitional days can be difficult to forecast and nuance, especially during springtime weather, but your best course of action is to watch how the weather is changing the snow surface throughout the day. If there is cold dry snow in your location, you should be dealing with primarily dry avalanches such as Wind Slabs or Dry Loose. On the flip side, if it’s sunny and warm or the snow surface is wet and sticky, you could be in wet avalanche territory. Watch out for Wet Loose or springtime shedding avalanches such as cornice failures or snow falling from rocky ledges. The size and frequency of these avalanches could depend on the duration of warmer temperatures or sunshine. Variability in the weather means conditions could vary between drainages or from aspect to aspect.

Broadly speaking, around 2.5-3 feet of generally right-side-up dry and settled storm snow exists over the 4/8 interface around the zone. In some areas, a more aspect-dependent snow surface has developed, with previous solar input driving the variability. Where this exists, slopes that have seen direct sunshine lately developed a surface crust of varying thickness and could contain debris from recent rollerballs or tree bombs. Below the surface crust, cold dry snow still exists above the 4/8 interface. Shadier slopes lack this firm cap and instead you will find the dry and settled storm snow. We do not anticipate any avalanches breaking into layers below the 4/8 crust at this point in time.

We have extended our forecasting due to the stormy weather to help you out. That means we still need you to share information with us by submitting public observations about what you're seeing out there. Help us build a better product for you.

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