Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Tue
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Another storm pulse will impact Snoqualmie Pass on Monday. Look for avalanche activity to peak during or shortly after periods of high precipitation rates or winds. You’re more likely to trigger a slide on wind-loaded features as you ascend in elevation.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Snowfall is slowly accumulating at Snoqualmie Pass and being drifted around by the wind. Look for wind slabs to develop on convex features, leeward ridgelines, in confined chutes/gullies, or near the base of cliffs. They’ll be larger and more reactive as you ascend in elevation and could be overlaying weak grains or a firm crust. Use small test slopes, uptrack tests, and quick hand-pits to gauge the new snow’s reactivity and bonding at the new/old interface.

    (3/10/2024)

    A skier-triggered slab in the Bryant Peak Couloir. This slab broke above and below the party.

Avalanche Discussion

NWAC will be closed on Tuesday, March 12th, as we gather and grieve following the death of one of our forecasters, Matt Primomo. We will not issue regular avalanche or mountain weather forecasts on Tuesday. We will return to normal operations on Wednesday, March 13th. We appreciate the community's understanding and support during this time.

Discussion:

We’re in the midst of a multi-day storm parade at Snoqualmie Pass. None of these storms are particularly large on their own, but when you group them together, the picture is a little different. Multiple rounds of precipitation, fluctuating freezing levels, and gusty winds coming from various directions have all influenced the 3/9 interface and the potential for avalanches on Monday. Avalanche hazard is slowly increasing as this storm pattern intensifies. Expect it to climb throughout the day and into the early evening hours. If temperatures warm, don’t be surprised to encounter rain resulting in rollerballs or other wet avalanche activity at lower elevations.

On slopes that typically receive direct sunshine, the 3/9 likely contains a melt-freeze crust of varying thickness. This could be a good sliding surface or result in the storm snow being poorly bonded. Before this cycle, weak grains, such as near-surface facets and surface hoar, were observed on shadier slopes. Where preserved, they could allow avalanches to fail easily or propagate widely. 

During Saturday’s convective showers, a lot of graupel fell at Snoqualmie Pass. Multiple backcountry travelers reported poor bonding just above the 3/9 interface due to these rimed precipitation particles. The distribution of graupel is often difficult to pin down, but it likes to gather in low places such as concavities, the base of cliffs, or where a steep slope starts to mellow out. Because of this, you might encounter slabs in a few unusual places on Monday.

Persistent slab issues continue to wreak havoc in neighboring zones. We do not have any confirmed avalanches at Snoqualmie Pass on the Early February Crust (EFC) or the associated interfaces, but that doesn’t mean it’s out of the realm of possibility. Remember this as we incrementally load our snowpack over the next few days.

Régions couvertes