Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Dangerous avalanche conditions will develop in all elevation bands by the end of the day as an atmospheric river impacts the region.  Deeper avalanches that break down to older snow layers will become more likely as the storm continues into Sunday night.  

Avalanche problems

  • Storm Slabs

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

    We have a recipe for storm slab avalanches on Sunday as dense new snow piles up, especially in the afternoon and evening, along with rising snow levels.  Shallow storm slab avalanches may break within inter-storm layers or on the old snow surface.  Strong S-SW winds will form deeper slabs in lee terrain near and above treeline.  

    Pay attention to signs of increasing instability like shooting cracks in the new snow, upside snow (denser over less dense), and new slab avalanches.  As the storm ramps up, reorient your travel plans to simpler terrain without exposure to overhead hazards.  Natural avalanches will become more likely towards the end of the day.  Smaller avalanches or cornice fall could step down to deeper layers for a more powerful and longer-running avalanche.  This is more likely on northerly and shady aspects at upper elevations that hold a colder and more layered snowpack.  

    Depending on how the storm cycle plays out, we may reach High Avalanche Danger Sunday night.  If you're headed out, make sure you're out of harm's way while this cycle plays out. 

    Steep terrain, fresh snow, and wind loading are all ingredients for avalanches in new snow layers. 

    Slabs will be deeper on lee slopes with strong S-SW ridgeline winds forecast. 

    Photo: Alpental Pro Patrol

  • Loose Wet

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

    New snow at lower elevations followed by rain will lead to wet loose avalanches.  While most wet loose avalanches will be small, in areas where the rain-line reaches higher following more significant amounts of new snow, or in areas where wet loose avalanches can gouge down into older wet snow,  larger and more powerful wet loose avalanches are possible.  This problem will stick with us through Monday as snow levels dance up to 6000'.   

    If you see natural wet loose avalanches or find yourself sinking into wet snow deeper than your ankle, move to lower angle terrain and steer clear of terrain traps that would amplify the consequences of a small avalanche.  Speaking of wet avalanches, anywhere you see glide cracks or evidence of recent glide avalanches, make sure to put an extra buffer between you and the suspect terrain.  Glide avalanches can release without warning. 

    (4/7/2023)

    Natural loose wet avalanches below rocky complex terrain. 

    Photo: Patrick O'Moore

Avalanche Discussion

It's that time of year when snowpack information from the East North is sparse and injects more uncertainty into our forecast.  If you're out in any part of the zone on Sunday - please submit an observation and let us know what you see.  

On Thursday night and Friday, areas east of Washington Pass (Harts Pass and Mazama) likely saw 2-5 inches of snow above 5000', with 2" or less near Washington Pass proper.  At the end of March, northerly aspects and upper elevations may have harbored weak snow surfaces. Snow that's slowly piled up in April may have bonded poorly to this older weaker snow layer.  Heading into this storm cycle, even though we're well into April, the avalanche conditions and snowpack are closer to that which we typically see in mid to late winter. Much of the snowpack is nowhere near transitioning to typical spring melt-freeze conditions.

Older observations: On Tuesday 4/4, Willie Webster went on an aerial tour of the zone and produced some great images of the current snow cover and recent avalanche activity. Notable were a couple of older avalanches including a very large natural slab avalanche on a NNE aspect of Silverstar Mtn and a natural glide avalanche on Hinkhouse Peak. See the photos below. On March 30th, Willie reported large debris piles on Harts Pass. The road was melting out quickly near Deadhorse Pt. He found a mix of sun crusts on the surface, though higher elevations looked to hold a cold, layered snowpack. 

Regions covered