Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 2 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The weak snowpack poses the risk of a low likelihood but high consequence avalanche. You can minimize your exposure to this hazard by avoiding steep and sustained open slopes on west, north, and east aspects. You’ll find safer travel and great snow in lower-angle terrain and in the forest.

 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2

    Weak layers of sugary snow, often interspersed with crusts, lurk beneath 1.5-3.5ft thick slab. This poor structure is well documented and has produced avalanches, whumphs, and poor test scores, all suggesting that a dangerous avalanche could ensue if you find the “sweet spot”. The likelihood of triggering a slide on these layers is low, but low probabilities don’t matter to the person who draws the short straw. 

    If you decide to roll the dice, stack the odds in your favor. Before committing to a slope, discuss the consequences of a slide on the terrain you are considering. Hedge towards simpler, smaller, and lower-angle. Choose planar and supported terrain with clean runouts and no terrain traps, only expose one person at a time, and minimize your exposure on the ascent. Keep in mind that areas where the slab is thinner, such as around rocks, trees, and locally wind-scoured spots may act as trigger points. Be wary of these specific features within wind-loaded start zones below ridgelines and cliff faces. Complex terrain often holds this dangerous combination of thicker and stiffer slabs with locally thin areas on the slope.

    A few other factors Wednesday: Look for small loose avalanches shedding from steep slopes and rocky faces in the sun. In addition, east winds are forecast to increase in the afternoon. Avoid lee start zones if you see actively blowing snow.

    (2/2/2025)

    This avalanche released after a audible whumpf. The slide failed on facets over a crust and released the entire width of the feature. NE, 3700ft

    Photo: Summit at Snoqualmie Professional Patrol

Avalanche Discussion

NWAC forecasters were out in the western and eastern edges of the zone on Tuesday. On the surface, they found hoar and facets on wind-sheltered slopes. Snow conditions were excellent on most slopes other than due south-facing terrain. Near ridgeline, they found slight evidence of wind-transport and thin wind slabs. As for the persistent slab, the theme of consistently inconsistent continues.

Mixed results on a northeast aspect at 3550' and 4400' highlight poor structure in addition to the variable presentation and distribution of weak layers and crusts within the snowpack. Another low-cut length PST adds to the body of evidence that shows that if you do initiate a fracture in the weak layer, it could propagate. While the PWL variability may be limiting reactivity and/or propagation width, there is lots of uncertainty, and we wouldn't hang our hat on that at all. Where there is poor structure, it isn't changing. The 1/10 complex and January Drought Layer are still weak, but as we get further out from the last load it is becoming more unlikely, though not impossible, to trigger an avalanche. That may change with a fresh round of wind and snow late this week through the weekend. In the meantime, stay humble and respect the inherent uncertainty associated with persistent slabs. There is tons of great and safe snow out there in mellow terrain!

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