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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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Avalanche potential is slowly increasing as we move toward the weekend. Look for red flag signs of instability, such as whumpfing collapses, shooting cracks, or recent avalanches, as indicators that the snowpack is reaching a breaking point. Slabs will be more likely on features over 35 degrees or wind-loaded terrain.

Avalanche problems

  • Storm Slabs

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

    Continued snowfall into Friday, combined with fluctuating freezing levels, will maintain concerns for storm slabs at mid and upper elevations. The higher you ascend, the larger they should be. Use small test slopes and uptrack tests to determine how the new snow is reacting to your weight. Take a moment to dig down to the topmost crust to look for potential failure points. If you find heavy snow over weaker snow, see shooting cracks, or blocks of snow failing in your tests, default to lower-angled terrain.

    Winds should be more robust on Friday than on Thursday, meaning there could be more wind slabs, especially at upper elevations where drier snow exists. Look for them on the leeward side of ridgelines or near rocky features such as confined chutes or the base of cliffs.

    (1/4/2024)

    The crown of a large natural avalanche that occurred at Alpental during a period of warm temperatures. [SS-N-D2-R2-O]

    Photo: Alpental Pro Patrol

Avalanche Discussion

It was a bit warmer and wetter at Snoqualmie Pass on Thursday than we had anticipated. This resulted in small natural avalanches at lower elevations running on the 12/30 crust. NWAC forecasters, Alpental Pro Patrol, and backcountry travelers reported similar conditions - moist snow, damp clothes, and a small avalanche cycle. The largest avalanche reported was a D2 slab by Alpental Pro Patrol. Others were small loose avalanches that failed in the moist snow. All slides allegedly ran on the 12/30 crust. 

We did squeeze out another 4-6 inches to cap the 4-7 inches from Wednesday. As we roll into Friday, expect more of the same. None of these storms are all that big, but if you add them up, we should have over a foot of new snow over the 12/30 crust before the main event on Friday night. Expect more wind and slightly cooler temperatures on Friday compared to Thursday. Of course, some models are calling for a brief temperature bump again - so be on the lookout for rollerballs and small wet avalanches if you experience rain falling on dry snow. 

As we roll into a stormy weekend, here’s some information on potential weak points in the upper snowpack, starting with the deepest:

  • Solstice Crust (formerly the 12/22 interface): The deepest layer of concern. It is roughly 1-1.5 feet deep. This crust/facet complex has been propagating in large column tests and has had our eye for about a week. It could produce the largest avalanches, and they could span far distances.
  • 12/25 crust: The next significant crust above the 12/22 complex. This layer was producing planar failures for professionals on Wednesday. It was not propagating in large column tests. This crust may not be distinguishable from the Solstice Crust in some locations.
  • 12/30 crust: A stout crust just under a foot down. It should be the sliding surface for most avalanches in the coming days and the focus of your investigations.
  • 1/2 interface: A layer of buried surface hoar may exist an inch or two above the 12/30. Where it exists, avalanches breaking on this layer could span far distances or wrap terrain features. There also might be near-surface facets around this depth in some locations. On Wednesday, Avalanche professionals received easy failures on this layer using tilt and compression tests.
  • 1/4 crust: Thursday's warmup will likely create a new surface crust for snow to fall on Thursday night and Friday. Its robustness will depend on how cold it gets.

Natural hazards continue to be a challenge and impede travel at lower elevations. Most open creeks and holes can be easy to spot, but not all. Travelers have been surprised by creeks that they never knew existed since we ordinarily play in a  deep winter snowpack. Stay vigilant out there.

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