Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Natural avalanche activity should taper on Thursday, leaving slopes primed for human-triggers. Dangerous avalanche conditions will exist as we transition out of this stormy period. Give the snowpack time to heal by avoiding all slopes over 35 degrees.

Avalanche problems

  • Storm Slabs

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

    Several waves of precipitation, fluctuating freezing levels, and strong winds have resulted in a layered upper snowpack. You’ll need to check the recent storm snow for weak interfaces and its bond to the old surface by digging. Small test slopes and uptrack tests won't cut it when the snow is this deep. Heavy snow over weak snow, layers of weak grains such as graupel, or wind-drifted slabs hidden below the surface are just some examples of potential failure points. Slabs should be larger as you ascend in elevation or in wind-loaded terrain. You’ll need to contend with storm slabs, wind slabs, and loose avalanches as you pick your way through the mountains. Regardless of the avalanche problem, you’re more likely to trigger one on slopes over 35 degrees.

    In isolated locations, natural avalanches could still occur. We wouldn’t be surprised to hear of an avalanche stepping down into old snow layers and growing very large.

    (2/28/2024)

    Debris from a large natural storm slab reached down into the trees below the main bench of Kendall Peak. SW 5400ft SS-N-D2-R1-U

    Photo: Dallas Glass

Avalanche Discussion

By Thursday morning, we should be on the tail end of a multi-day storm cycle that dropped several feet of snow at Snoqualmie Pass. Temperatures, wind speeds, and precipitation rates should all decrease. That leads us to believe that widespread natural activity will likely have passed by the time day breaks, allowing us to lower the hazard rating. 

That doesn’t mean it’s not dangerous out there. On Wednesday, Alpental Pro Patrol, avalanche professionals, and NWAC forecasters observed natural avalanches large enough to bury and kill you. Slabs were reportedly touchy to human-triggers and failed at the newly formed 2/27 interface, even in treed areas commonly thought of as "safe". One common theme was that even small avalanches ran far distances, surprising professionals. You’ll have plenty of new snow problems to deal with on Thursday.

The biggest uncertainty piece revolves around if you have older snow problems to deal with. Before this stormy week, a series of crusts interspersed with pockets of weak snow existed above the Early February Crust (EFC). NWAC forecasters have found weak grains sitting on the EFC as recently as Tuesday. To date, we do not have any confirmed avalanches on these older weak layers. This has been a major loading event and could be the one to start to tip the scales.

After such a snowy week, snow immersion suffocation (SIS) can be a real hazard. Keep your partners in sight and know the risks. You can learn more here.

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