Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

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

Despite the less than impressive forecasted precipitation, with weak snow in the upper snowpack, don’t be surprised if you trigger shallow slab avalanches. Use hand pits and uptrack tests to look for strong over weak snow. Don’t let one of these small avalanches shove you over a cliff or into a creek.

Avalanche problems

  • Storm Slabs

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

    This isn’t a very big storm for the Pass, but the upper snowpack has several possible weak layers. This could lead to a rather complex situation that differs by aspect and elevation. You’ll need to look frequently into the snow to see if you have strong over weak layers. Use simple hand pits, uptrack tests, and small slopes to see how the snow reacts. When it fails easily, you’ve found the storm slab problem. You may find layers break within or at the base of the storm snow. However, they could also fail on weak sugary facets that sit just above the very prominent Early March Crust. These persistent grains are most common above 4500’ on NW-NE aspects and could allow these shallow slabs to break widely. Fortunately, any resulting avalanches should stay rather shallow and small. Don’t let one of these slides catch you by surprise and push you into a terrain trap.

    (3/12/2022) Hand pits and hand shears can help you check for strong over weak snow in the upper snowpack, Photo: Dallas Glass

Avalanche Discussion

The first in a series of storms will impact the Pass Saturday night into Sunday. With the upper airflow more from the South, Snoqualmie shouldn’t receive as much precipitation as some other locations. Unfortunately, it looks like mostly rain at Pass level, but it should quickly turn to snow as you ascend. Near and below this rain-snow line, you could encounter the possibility for loose wet avalanches. However, this low elevation snowpack has been through a lot this winter and should handle this modest amount of rain without a significant issue. Instead, it could only make for challenging travel with wet heavy snow, slick surfaces, open creeks, and frozen piles of avalanche debris.

Above the rain-snow line, we’re mainly concerned about the upper snowpack sitting on the thick and prominent Early March Crust. Prior to this storm several warm and sunny days allowed the snow surface to become wet and sticky. That likely created a new crust (3/12) on which the storm snow will accumulate. This crust should be thicker on southerly aspects and much more breakable on shady slopes. Weak sugary facets (1-1.5mm) were observed in several locations around the Pass. You’re most likely to find these persistent grains on NW-NE aspects above 4500’ just above the Early March Crust. Up until now, there wasn’t much of a slab on this potential weak layer. Will this storm be enough to cause that to change? We’ll see.

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