Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

A sustained east wind event wreaked havoc on the Pass's snowpack but also localized the danger to wind-loaded areas. Be leery of smooth pillow-like drifts along exposed ridges, near the base of cliffs, in the tops of chutes, and even on some mid-slope features.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Moderate avalanche danger with a wind slab problem is a pretty common forecast here in the PNW. However, over the past two days (Fri/Sat), we’ve received reports of 8 or more unintentionally triggered wind slab avalanches catching travelers off guard. Thankfully, none of these events resulted in injuries or death, despite some very consequential terrain. This speaks to the unique nature of these particular wind slabs. 

    Sustained E winds loaded unusual slopes. So, while you may see signs of wind effect in lots of places, you really want to look for firmer smooth slabs. Take note of scoured slopes, textured surfaces, and sharp drifts that highlight local wind patterns and point toward potentially loaded slopes. 

    Sometimes, wind slabs are hard to assess. They may not react the same from one spot to the next. Small slopes can give you a glimpse of how they might respond, but the recent avalanches suggest they might not give you the full picture. Seek out more wind-sheltered terrain to avoid this issue.

    (2/16/2024)

    An unintentionally skier-triggered wind slab in a confined rocky chute. Note the textured surface up against the rock wall.

Avalanche Discussion

The easterly winds should calm down a bit Saturday night and Sunday. However, the damage is already done. The few inches of new snow that might fall by the afternoon could only mask some of the more subtle wind slab clues. 

We’ve already talked about the unusual loading pattern, but there are other aspects of the upper snowpack that could make this setup different. Over the past few days, Avalanche professionals have reported significant test results on differing layers in the upper snowpack. Some of these occurred on thin crusts, some on layers of facets, and other facets above the burly Early February Crust (EFC). These results haven’t been consistent, but they catch our attention. It highlights the potential for more surprising avalanches failing slightly deeper in the snowpack. These slides would still generally be isolated to wind-loaded terrain, but they could fail above you or break widely. 

There are a few notable avalanche observations from the Pass. On Friday, wind slabs were triggered in both the Slot and Snot Couloirs on the N side of Mt Snoqualmie. Additional small natural wind slabs were noted in rocky unsupported terrain in the Chair Peak Lake basin. 

On Saturday, an NWAC forecaster traveling in the Alpental Valley reported a sun crust on more sheltered southerly aspects, soft snow on north-facing terrain, and tree debris from the recent winds everywhere. Good travel conditions in shaded, sheltered areas continues to be a common theme. Elsewhere, open creeks, breakable crusts, icy scoured slopes, and exposed obstacles continue to plague travel, particularly at lower elevations.

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