Lawinenlagebericht

Snoqualmie Pass

Northwest Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

We're in for a pattern change at Snoqualmie Pass on Tuesday. Sunshine is expected to replace the snowy and windy weather, possibly increasing avalanche potential. Keep an eye on the snow surface to see how it changes throughout the day, and head for shaded slopes if you see natural activity.

Lawinenprobleme

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Bring on the March sunshine! We're listing this problem as Wet Loose, but the assumption is that we could see various solar-assisted avalanche problems on Tuesday. To start, solar input will likely result in snow shedding from trees and rocks, possibly triggering loose avalanches on the slopes below. These will probably be more dry than wet. The longer the sun stays out, the more loose avalanches could transition toward "moist loose" and eventually reach the wet threshold. Elevation could play a role in avalanche character as well. Lower elevations will be more likely to reach wet status and have a good bed surface for slides to run on.

    More concerningly, the snow could also "slab up" on slopes that receive direct sunshine. Public observations indicate this happened on Monday on the southerly slopes of Mount Snoqualmie. Loose avalanches could also trigger lingering slabs as they descend.

    In the end, the moisture content doesn't really matter. If you're on a sunny slope and see signs of natural avalanche activity, head for shadier aspects where this problem is less likely. On steep, shaded aspects, you may be able to trigger dry loose avalanches in the low-density snow, although the lack of a good bed surface and continued settlement should help keep them in check.

     

     

    (3/3/2024)

    Dry loose avalanches coming out of a steep and rocky area on Kendall. These slides may have resulted from snow shedding from trees and rocks during a period of sunshine.

    Photo: Andy Harrington

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Wind slabs may still be reactive to human triggers as you ascend in elevation. Numerous slabs were triggered over the weekend on features such as the base of cliffs, convex rollovers, and the tops/sides of narrow chutes. You may notice textured surfaces or large drifts indicating wind loading. As alluded to above, the introduction of March sunshine could increase the reactivity of these slabs on slopes that see direct sunshine. If you suspect that a slope is wind-loaded, choose a different path.

    (3/2/2024) 

    A skier triggered wind slab avalanche on a convex slope on Mount Snoqualmie. There's also evidence of dry loose in this photo.

Avalanche Discussion

Morning sunshine and calm winds are forecast for the Snoqualmie Pass zone on Tuesday. This will be quite the pattern change from what we've experienced over the past week when multiple days of low-density snow and strong winds were the norm. As mentioned above, that low-density snow is now being subjected to the strong March sunshine, which could play out in several ways. On Monday, backcountry travelers on Mount Snoqualmie reported that the snow started to "slab up" due to solar input, and they easily triggered 4-6" slabs on southerly aspects receiving direct sunshine. This process could expand to more slopes on Tuesday. We also wouldn't be surprised if clouds move in, resulting in minimal avalanche activity. This is Snoqualmie Pass, after all.

The snowpack at the Pass is elevation-dependent, and the magic line is roughly 4500 feet. Below this elevation, up to a foot of recent storm snow sits above a stout crust. Above it, the crust dissipates, and deeper storm totals exist. On Sunday, NWAC forecasters found roughly 2 feet of settling and right-side-up storm snow from this past week. Weather station data indicates strong settlement rates, meaning the storm snow is gaining strength. Over the weekend, there were numerous human-triggered avalanches reported on wind-loaded features. 

It’s worth noting that most of our neighboring zones are dealing with a persistent slab problem (East Central, East South, West South, Stevens Pass). In these areas, slides are failing on deeper layers at or just above the Early February Crust (EFC). We do not have any confirmed avalanches on this layer at Snoqualmie Pass. However, you should at least consider the possibility of a very large persistent avalanche if you're heading for big open slopes. On Sunday, NWAC forecasters found the EFC 5 feet below the surface in the Kendall area.

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