Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

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

Easterly winds will load lee slopes as the snow falls, creating reactive slabs large enough to injure you. Check for slab depth and reactivity using hand shears and representative test slopes. Identify and steer around open slopes 35 degrees and steeper with more than 6" of snow on the crust, actively drifting snow, or lens-shaped pillows.

Avalanche problems

  • Wind Slabs

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

    A fresh round of 2-5" of snow falling during the day on Monday allows moderate to locally strong SE winds to reverse load avalanche start zones and mid-slope features. The snow will fall with increasing density as temperatures slowly rise during the day on Monday, creating a shallow upside-down layer by the end of the day. However, most slabs will occur within wind-drifted snow. You'll want to steer around slopes 35 degrees and steeper anywhere you suspect deposits of 6" of fresh snow deposition. In some areas, these deposits sit directly on and may bond poorly to a very slick crust. In other areas, they may rest on old snow. Keep in mind that older slabs likely formed on typical aspects, while the fresh slabs will favor the eastern half of the compass. Be suspicious of slopes below fresh, sharp cornices and where winds redistribute snow from the windward to the leeward side of ridges. Before committing to any steeper open slope, it's a good idea to take advantage of representative test slopes to assess the bond of potential slabs to the crust and/or old snow interfaces.

    Avalanches could build up to size 1.5 at middle and upper elevations. Your risk of injury increases due to early season hazards. Taking a ride could mean being raked through rocks, downed tree limbs, or frozen avalanche debris.  At lower elevations, you might find wind deposits in the terrain, but in most cases, early-season conditions make these slabs very isolated. Thus, it's important to note when snow slopes become smooth enough for avalanches to become a problem.

     

    Example: Signs of wind loading to look for on Monday.

    Photo: Dallas Glass

Avalanche Discussion

Avalanche hazards will increase throughout the day as a storm ramps up. Temperatures will be chilly with a biting windchill, so bundle up even at pass level. However, there is the chance that some areas not far west of the pass could transition from snow to rain up to middle elevations. If this occurs in your terrain, expect small loose snow avalanches that can run on a crust. Avalanche hazard may be locally higher than forecast and you should limit your exposure to open slopes above you.

Near the pass, the snow (potentially mixing at times with freezing rain) falls on top of 8" of settling storm snow, sitting above a crust. By the end of the day Monday, there could be a foot of snow above the crust in some areas. Clear skies Friday night may have formed some weak interfaces that could get buried in the most wind-sheltered areas. If we do get closer to the upper end of our expected 2-5" of snow, you could get a storm slab to release by late in the day on a sheltered, open slope. Whether you're navigating around wind slabs or one of these sheltered slopes, it's a good idea to test the upper foot of the snowpack for the shear quality of interfaces. 

 Although the E winds were blowing on Sunday, Alpental Pro Patrol reported minimal snow available for transport. Observers on Saturday found widespread evidence of recent strong WNW winds in exposed terrain.  Firmer textured snow, wind lips along ridgelines, and scoured surfaces were easy to find.  1 thin natural slab avalanche on the N side of Kendall Pk may have occurred Friday evening during heavy snowfall.  In steeper terrain scoured to the old crust, travelers reported a slick icy surface to contend with. 

It will take a larger storm to significantly improve the low snow travel hazards. Creeks, rocks, logs, trees, and frozen old chunky debris all exist and can make even easy travel routes quite treacherous and time-consuming. Give yourself time to deal with the persistent early-season conditions. 

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