Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Shifting winds during the week easily moved low density (lighter) snow and may have cross-loaded open slopes at mid and upper elevations.  Where you find wind-drifted snow, consider the consequences if you trigger a shallow slab avalanche before committing to a slope.  Despite building snow depths, creeks are still open and a travel hazard at low elevations. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Shallow human triggered soft slab avalanches have been reported the last 2 days in the Alpental Valley following several days of light low-density snowfall and moderate/strong ridgeline winds. On Thursday, observers noted ongoing wind transport in the Snoqualmie Pass area near and above treeline.  With a switch from E-SE winds earlier in the week to westerly winds on Thursday, there's the potential for cross-loaded slopes. 

    Visual clues like fresh cornices may be less help than usual, so consider any steep open slope with wind-drifted snow suspect.  Observe how the snow stiffness and texture change across aspects and elevations.  You can always choose more sheltered or lower angle terrain to avoid the problem.   

    Anywhere the snow remains light and fluffy, anticipate small Dry Loose avalanches that can run fast and surprise you in steep, rocky terrain.

    (12/15/2021)

    Many wind features and a few softer wind slabs in the rolling terrain above Nash/Snake Dance in the Alpental Valley.

    Photo: Anna C

Avalanche Discussion

Another 3-4 inches of snow fell during the day on Thursday with estimated moderate to strong westerly ridgeline winds.  This is on top of the 3' feet of snow that fell at Pass level since temperatures cooled last weekend, with even more at higher elevations.  A steady trickle of observations continue to report shallow human-triggered soft slabs below ridgelines or on open slopes at mid elevations as well as signs of instability like cracking in wind-drifted snow.  Observers have reported a generally right-side-up snowpack below treeline.

Deeper in the snowpack, we are tracking a thin crust (12/8) about 4-6” above the icy block at the bottom of the snow. In the nearby Stevens Pass and the West South zones, small weak facets were observed near this crust. So far, we have not confirmed any avalanches on this layer. However, if you dig in the snow, see if your snowpack tests fail suddenly or slide easily on weak grains around the crust.

The early season snowpack is relatively variable and can change by aspect, elevation, and location. The snowpack formed very recently and observations have been limited to mid-winter. As you approach new terrain, small test slopes can help you gather information before stepping out into larger and more consequential terrain.  Also, consider giving yourself a margin of safety as you travel near smooth rock slabs such as this frequent flyer at Alpental which released an avalanche to the bedrock early on 12/14.

Open creeks are still an ongoing hazard to backcountry travelers at lower elevations. Choose your travel routes and creek crossings carefully.

Regions covered