Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Avalanche danger will increase as a storm deposits over a foot of snow Saturday night, which will be accompanied by wind. Pay attention to clues such as long shooting cracks or whumphing,  or any thicker-feeling deposits of snow, and steer around steep slopes if you see these indicators or have any doubts. 

Avalanche problems

  • Storm Slabs

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

    It is likely that you could trigger a slab avalanche after an overnight storm Saturday night into Sunday brings heightened avalanche concerns. An avalanche is most likely to occur in areas where wind deposited snow into thicker drifts, such as along ridgelines, around outcroppings, or in gullies. Strong winds are expected to redistribute snow during this storm, especially at higher elevations.  However there could be enough snow, even in non wind-loaded areas, that you could trigger an avalanche.

    Clues such as long, shooting cracks running from your feet or snowmobile are good indicators of an unstable snowpack. Hearing or feeling a whumph, or seeing large collapses not just underneath you but stretching several feet away from you are other indicators that an avalanche is likely to occur on slopes steeper than 35 degrees. Snow that feels stiffer, or upside-down (a harder surface and softer beneath), are signs that the snow may avalanche on a steep slope. If you find any of these signs, stick to lower-angle terrain. 

    An example of a storm slab avalanche, triggered on a steep rollover. Photo: Phil Straub

Avalanche Discussion

Minimal preexisting snow was present in below treeline areas, although a foot or more of snow is expected to fall even to lower elevations Saturday night. Isolated lower elevation locations which already held enough snow to form a smooth surface, or low shrub/grassy surfaces, are probably the only areas where smaller avalanches might occur below treeline on Sunday.

Previously, a snowpack of 2-3 feet sat under high pressure from Nov 8 - Nov 21. Weak, faceted crystals formed in shady areas. Meanwhile, hard, sun-affected surfaces developed on south-facing slopes. Upper elevation treeless terrain was buffeted with wind from all directions, so fewer pockets of weak snow developed on shady aspects here.  Isolated, shady and sheltered areas could still harbor weak snow, but we have limited information about its presence at the time. 

Despite this last storm,  it's still early season, and the snowpack is shallow. Lots of early-season hazards exist such as shallowly buried trees, rocks, and other obstacles. In terms of our snowpack, we're still gathering information about what's out there on the ground, so this forecast comes with a fair amount of uncertainty with limited information as a starting point. If you make it out on Sunday, don't hesitate to submit an observation. Information about any avalanches that you saw or triggered, thicknesses of new snow, or the entire snowpack depth in more areas is incredibly helpful for us. 

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