Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

On Friday, you should steer around wind-drifted piles of snow at upper elevations where triggering an avalanche is more likely while taking note of how the snow surface is changing throughout the day due to the sun’s influence. If you find yourself in full sunshine and notice recent avalanches, dangerous avalanche conditions may have developed and you should head toward shaded slopes.

Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Partial sun combined with springtime temperatures could have enough influence to drive Wet Loose avalanches on Friday. Keep an eye out for rollerballs and pinwheels or the snow surface getting warm and sticky as indicators that the snow surface is destabilizing. If you notice these signs, natural Wet Loose avalanches may follow or you may be capable of pushing snow downhill to create Wet Loose avalanches of your own. These avalanches will be more likely depending on the amount of sunshine that can make its way through the clouds and tend to develop on slopes that see direct sunshine. Wet Loose avalanches often start at a point and can entrain snow, fan-out, and even trigger slabs as they descend downhill. You can minimize your exposure to these avalanches by heading toward shadier slopes and ensuring that the slopes above you are not in the sunshine.

    (3/13/2021) Wet Loose avalanches such as this one may be more widespread in areas with more sunshine on Friday. [3/13: Faraway Rock, SE aspect, 5000'. WL-N-D1.5-R1-I]

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Continue to keep an eye out for Wind Slab potential as you ascend in elevation on Friday. Recent snow totals vary around the zone, but most areas are reporting wind-effect at upper elevations with deposits much deeper than reported snow totals. You should use test slopes, uptrack tests, or visual clues such as freshly built cornices or textured snow surfaces to help you determine the existence and reactivity of potential Wind Slabs. Convex rollovers, terrain features over 35 degrees, or rocky terrain including confined gullies or the base of cliffs, are the more likely locations for you to trigger one of these slabs on Friday. If you find a poor bond during your testing or notice cracking in the recent snow as you travel, look to avoid these features.

    If you come across freshly built cornices due to the recent storm, they may be sensitive so give them a wide berth by not traveling on or below them.

    (3/20/2021) Using visual clues is a great way to help identify the potential for Wind Slabs.

Avalanche Discussion

The recent storm created the 3/24 interface and favored the volcanoes, where close to 10” of snow fell, with lesser totals near the crest.  On slopes that see direct sunshine, this interface along with the deeper 3/18 interface should be easily identifiable. These interfaces may be a bit more subtle on slopes with a northerly component, but you should still be able to find them in your pits. We believe that all avalanche activity on Friday should occur above the 3/18 interface, with most focused above the 3/24. However, slopes may act differently depending on the aspect and surface the recent snow fell on, so be sure to choose representative testing locations. 

Mostly cloudy skies kept a widespread natural Wet Loose cycle at bay for most of the West South on Thursday, but the new snow didn’t fully escape the sunshine. Snow surfaces got warm and sticky, producing some rollerballs, treesbombs, and isolated Wet Loose avalanches on slopes that often see direct sunshine. Areas further to the South such as Mount St. Helens may have seen more blue sky and therefore, a more widespread Wet Loose cycle. With mostly cloudy skies forecasted, look for similar conditions on Friday. However, cloud forecasting can be difficult and we have a large zone, so you should be prepared to change your travel plans if the cloud forecast doesn’t verify and you find yourself in full sunshine. This could lead to a more widespread and dangerous Wet Loose avalanche cycle.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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