Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 2 years ago.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

Highlights

The weather may be calming, but the snow continues to fall, the wind keeps blowing it around, and dangerous avalanche conditions persist. Expect the likelihood and size of any avalanches to increase with elevation and exposure to the wind. Ease into the terrain, consider steep slopes guilty until proven innocent, and give a wide margin to wind-loaded areas at the upper elevations.  

Avalanche problems

  • Storm Slabs

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

    A pulse of snow overnight into Monday morning could deliver another 6-10 inches to the Pass, on top of the 2-4” that fell during the day on Sunday. While this is enough snow to warrant caution on any steep slope, we are especially concerned about wind-exposed terrain where these slabs will be deeper, harder, and more reactive. The new snow rests on a variety of surfaces: a rain crust at the lower elevations, a firm interface around 4500 to 5000’, and potentially deeper and less consolidated snow at the highest elevations. You’ll need to assess the bond between the new snow and the interface below, as well as any weaknesses within the new snow. While we expect most avalanches to involve snow from Sunday and Monday, we can’t rule out a deeper slide, especially in wind-loaded terrain at the upper elevations. Tread carefully around unsupported terrain, slopes below sharp ridgelines, convex rollovers, and gully entrances where slabs tend to lurk.

    Use a pole or your hand to track the depth of new snow over the firmer interface below and dial it back in locations where the snow is deeper. Identify slabs by feeling for hard-over-soft snow and watching for signs like blowing snow, textured surfaces, or chalky drifts. Before committing to steep terrain, use hand pits, uptrack tests, or safe test slopes to check stability and look for red flags like shooting cracks and recent avalanches. Remember that these informal tests only reveal conditions as deep as your ski, sled, or hand can dig. In wind-loaded zones, the safest choice is to give the snowpack an extra day to adjust to the new load.

    A slab avalanche breaking on a steep slope at a gully entrance.  This would be a prime location for an avalanche on Monday.

    (12/16/2024)

Avalanche Discussion

The storm train keeps rolling, bringing the running water talley to 6" since Christmas Day. To change it up a bit, precipitation from Sunday evening through Monday should fall as all snow, even at Pass level!

The snowpack has been through a lot over the last few days and conditions vary considerably at different elevation bands. We haven't heard much from the upper elevations, but we expect a whole different world up there compared to what happened below 5000-5500'. If you venture that high, you'll need to be heads up and consider that avalanche conditions could change sharply as you find deeper and drier snow from the past few days.  

On Sunday, Alpental Pro Patrol reported a firm 12/28 interface all the way to the summit at 5470', with 3" of well-bonded new snow above the crust as of 4 PM. Meanwhile, a backcountry party in the area found the 12/28 interface to be a bit softer (ski, but not boot supportable) above 4500'. They triggered 3-5" deep reactive storm slabs on steep slopes at the upper elevations, running on this interface. Their observation ahead of  another shot of snow overnight is reason to treat slopes with caution unless you can confidently assess otherwise on Monday. Consider that the nature of the new snow and the interface below could change with suddle shifts in elevation and even slope to slope at similar elevations.

Adding to the uncertainty with Monday's forecast, Puget Sound Convergence Zones are tricky to forecast and the weather models aren't in great alignment for overnight totals at the Pass. The bottom line on Monday is that the more new snow we receive, the higher the liklihood and consequence of any potential avalanche activity. Check NWAC weather stations on Monday morning and assess the snow depth once you are in the mountains and adjust your plans as needed.  

Enjoy the break in the action Monday and Tuesday and please send us an observation if you make it out!

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