Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Incoming snow and wind should drive an uptick in avalanche potential on Tuesday. Keep an eye out for unstable pockets of wind-drifted snow on leeward slopes near ridgelines or near rocky features such as cliffs and gullies. Taking a quick look at how the new snow has bonded to a variety of surfaces should help you to select appropriate terrain.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    The most likely location for you to trigger a slab on Tuesday will be in wind-loaded terrain at mid to upper elevations. Look for actively blowing snow to help you identify where shallow Wind Slabs may be forming. Other visual clues such as fresh drifts behind natural objects or textured surfaces are indicators that the wind has affected the snow in that area. We expect any potential Wind Slab to be on the small side, but the bonding may vary from slope to slope depending on the existing snow surface. Take some time to check the base of the new snow to see how it has bonded by using quick hand pits or test slopes as you travel. You should steer around steep features over 35 degrees that you suspect are wind-loaded or if the new snow has not bonded well to the underlying surface. 

    (2/26/2022)

    This shallow slab failed on some weak snow prior to the atmospheric river event. Similar slabs on convexities or leeward sides of ridges could exist on Tuesday.

    Photo: Public Observation

Avalanche Discussion

Snow showers and gusty winds should impact the zone throughout the day on Tuesday, with snow rates highest in the afternoon hours. This will bring a change from the wet avalanche problems we have dealt with over the past week back to dry, new snow problems. Last week’s atmospheric river event dropped 9.5” of water on the zone, much of which was rain, resulting in a significant avalanche cycle. A few inches of cold dry snow fell in the days that followed and was weakening (faceting) on shady slopes over the weekend. The effects from this time period are still visible throughout the zone with avalanche debris, open creeks, rain runnels, and a variety of snow surfaces. 

Why is this important? These various, and in places rough, snow surfaces will help dictate the ability for avalanches to fail in the coming days. In areas where the new snow is poorly bonded or overlaying weak snow, such as on shady slopes, slabs could be more touchy. On the flip side, if new snow is falling on a pile of hard avalanche debris, you’ll be hard-pressed to get a new slide going. On slopes where a firm smooth crust exists, such as on slopes that see direct sunshine, a poor bond could mean that dry loose avalanches composed of the new low-density snow are able to run far and fast. There isn’t that much new snow expected, so taking a moment to look at the bond and previous snow surface on the slope you are traveling shouldn’t take too long and will help you make a better slope-specific forecast. We do not have any layers of concern below the current snow surface. 

Additionally, this storm shouldn’t be enough to bury all of the natural hazards that the atmospheric river exposed, so tread carefully and don’t get tripped up in consequential terrain.

Regions covered