Avalanche forecast

West Slopes North

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Temperatures are finally cooling but a lot of water fell, much of it as rain even to near treeline elevations, and natural large wet snow avalanches are likely. Avoid traveling on steep slopes, and take extra care to limit time beneath large avalanches paths and gullies even below treeline, since there's a chance large, destructive avalanches could run from above. If you're above treeline, strong wind gusts redistributed the snow that fell, forming thick slabs which we recommend avoiding on steep slopes as it's likely you could trigger an avalanche in these drifts. 

Avalanche problems

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5

    You may see a number of wet snow avalanche problems lingering near and below treeline as the peak intensity of this atmospheric river slows. We are most concerned about wet slab avalanches, as they are very unpredictable and could be deadly. These generally only happen naturally and without warning in areas where the rain saturated deeper into the snowpack. If the top foot or more of the snow is wet, steep slopes could slide as a large slab avalanche. Avoid steep slopes in areas where water saturated down into the snowpack. 

    The West North zone has an abundance of terrain suitable for glide avalanches, like smooth rock slabs and grassy or low-shrub-covered steep slopes. Glide avalanches are primed to fail right now as well. They also will likely not provide a hint as to when they'll slide, although you could see glide cracks indicating snow is slowly shifting downhill and could rip out down to the ground without warning. Avoid traveling beneath glide cracks. With any of these wet snow avalanche concerns, be very aware of terrain up above you, even if you're on a low-angle slope or crossing a gully below treeline. If a large path sitting above you avalanches, it could send heavy, wet, damaging debris down towards you. 

    Wet loose avalanche activity will likely decrease as temperatures cool, but you may still encounter them near treeline where previously dry snow became wet. 

    (1/14/2022)

    An old photo of natural wet slab avalanche triggered by heavy rain last week above Schriebers Meadow, similar to what you might see Monday.

    Photo: Graham Clark

  • Wind Slabs

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

    Much of the storm's precipitation fell as rain below 4000-5000ft, although the final intense burst which arrived Sunday afternoon may have pushed snowlines even a little higher. At elevations above the wetted snowpack, you'll still find dry snow which was redistributed with strong winds. Search out signs of wind-affected snow, like shaped features, large pillows, or textured surfaces. Feel for heavier snow. If you find any of these clues, steer around nearby steep slopes.  Use obvious red flags like long shooting cracks or recent avalanches as indicators to avoid steep, wind-loaded slopes as well. 

    (4/3/2023)

    Small wind slab pockets like ones that you may be able to trigger above treeline on Monday. Note the wind featured surface and deeper looking drifts you can identify along the ridge, where the avalanches occurred. NNW, 6000ft in the Canyon Creek area. 

    Photo: Hans Brubaker

Avalanche Discussion

Cornices have likely weakened with the recent warm temperatures and precipitation. Stay far back from their edges and away from slopes beneath them. 

Natural or human-triggered avalanches could occur below treeline, although they'll likely be smaller. Our main concern at these lower elevations is larger avalanches running from higher elevations. Even if you're on a road or trail where there isn't any snow, if there's steep, snowy slopes up above, even if you can't see them, there's a small chance an avalanche could still run down a gully and impact the trail or road. In February an avalanche trapped a vehicle on the uphill side of Church Mtn Road off Highway 542, but thankfully no one was beneath the gully when the wet heavy snow came plowing down.

Since Thursday the Heather Meadows weather station has received nearly 6" of water, much of which has fallen as rain at that elevation. A little higher, more of it fell as snow. Only about half that amount fell in other areas further from the volcano in the zone. Wet snow avalanches have run in the backcountry in most areas, up to D2 (large) with this storm. Not many people are out right now to witness the extent of avalanche activity with this last warmer burst of precipitation, but we suspect to see evidence of more large wet avalanches which ran naturally in the coming days. Extent of avalanche activity likely varies throughout the zone. Residual wet snow problems will remain a problem for the next couple days while the snowpack drains. 

 

 

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