Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

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

Continue to remain suspicious of wind-loaded slopes on Thursday as another round of stormy weather impacts the Snoqualmie Pass zone. Actively blowing snow or red flag signs of instability such as shooting cracks or whumpfing collapses should help steer you away from slopes over 35 degrees. 

Avalanche problems

  • Wind Slabs

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

    Wind-affected snow will remain the most likely location for you to trigger an avalanche on Thursday. More snow and wind should help to thicken any pre-existing slabs or build fresh slabs on leeward slopes. Although the largest and potentially more sensitive slabs could be found at upper elevations, don’t overlook smaller features well below ridgecrest that are prone to wind-loading. Be leery of convex rollovers, confined chutes and gullies, or the base of cliffs where the wind likes to drift the snow into deeper piles and avalanches like to initiate. Using visual clues such as textured surfaces or smooth pillow-like piles of snow can help you identify wind-loaded slopes to avoid. You can gain information about slab potential or weak layers in the new snow by using uptrack tests or small test slopes. If you suspect that a slope is wind loaded or find that blocks of snow are failing easily in your tests, head for slopes under 35 degrees.

    On slopes with a more northerly aspect, a poor snowpack structure has been identified. More details surrounding these areas are in the discussion below, but you should be aware of the possibility of isolated avalanches breaking in surprising ways.

    (2/1/2022)

    A small wind loaded test slope failed and cracked easily.

    Photo: Dallas Glass

Avalanche Discussion

Recent observations from the pass indicate that the wind has been a player in drifting snow and sculpting the landscape since Sunday night. Professionals and recreationalists alike have noted textured surfaces, shallow slabs, and freshly built drifts and cornices. There have not been a lot of recent large avalanches observed, but smaller slabs and some dry loose avalanches have been reported on steeper slopes. Generally speaking, the recent snow is moderately well bonded to the Late January Crust (1/30). 

Below the surface, a poor snowpack structure including a facet-crust combo has been identified on slopes that contain a northerly tilt. It is believed that the slab depth over this weak interface has not yet grown to a critical point to produce avalanches, but we will be watching this set-up for the foreseeable future. As we incrementally increase the load atop this layer, it’s a bit of a waiting game to see if it starts to come into play. Our sense is that the new wind and snow on Wednesday night and Thursday will not be enough to tip us over the edge, but you should be sure to do your homework before stepping into consequential terrain. If this layer starts to produce avalanches, they may break in surprising ways and span farther distances than you’re used to, connecting terrain features. Due to its uneven distribution, you could find that adjacent slopes are behaving very differently.

As the day progresses on Thursday, a slight rise in temperature is expected. Precipitation should be tapering by the time this happens, but we can’t rule out some rain or mixed precipitation at lower elevations. Areas in the western part of the zone come to mind as a more likely location for liquid precipitation. If you find rain falling on cold dry snow, start to put some wet avalanches on your radar on slopes over 35 degrees. Also take note if heavy snow starts to overlay weaker snow, resulting in more widespread storm slab issues. You can check for and manage these avalanches with many of the same tests as Wind Slabs.

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