Bulletin d’avalanche

East Slopes North

Northwest Avalanche Center
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Danger d’avalanche

Tue
Alpin
2 · Modéré
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Points saillants

Dangerous avalanche conditions and natural avalanches are possible at all elevations Sunday night.  Mild weather and rain at lower and mid elevations will extend the threat of large wet avalanches on Monday.  Glide avalanches may release without warning, so put distance between you and slopes with glide cracks. 

Problèmes avalancheux

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Continued mild temperatures and a snowline between 5000-6000' will keep wet loose avalanches in play on Monday.  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.  

    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

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Dense wind slabs likely formed Sunday and Sunday night above treeline (and the rainline).  With lighter winds and snow expected on Monday, the likelihood of natural slab avalanches will decrease. 

    However, you can still trigger an avalanche in recently wind-drifted snow.  These slabs likely formed on the downwind side of ridges, below cornices, and under cliffs. You can use visual clues such as blowing snow or sharp cornices forming to help you identify slopes of concern. Shooting cracks under your feet are direct signs of instability and means that you're likely to trigger an avalanche on similar steep slopes. 

    Smaller slab 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 held a colder and more layered snowpack prior to this storm cycle.  

    (4/8/2023)

    Large avalanche from a human triggered cornice fall on Saturday.

    Photo: Mission Ridge Ski Patrol

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 the mountains, submit an observation and let us know what you see.  

An atmospheric river brought about 0.30"-0.50" of water to weather stations through 6 pm Sunday near the Cascade crest with a snow level likely somewhere between 5000-6000' along with moderate to strong SW ridgeline winds. Prior to the warm-up,  a few inches of snow fell Thursday night and Friday above 5000'.  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, the avalanche conditions and snowpack were closer to that what we typically see in mid to late winter. 

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.  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. 

Régions couvertes