Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

If you’re going to find an avalanche issue, it will likely be in small pockets of wind drifted snow. Due to the recent east winds, some of these slabs may occur in some unusual locations. Look for textured surfaces and fresh drifts to point out which slopes you may want to avoid.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Two things make this wind slab event a bit unique: easterly winds and extremely cold temperatures. East wind events like we saw on Tuesday frequently produce very irregular and unusual loading patterns at Snoqualmie Pass. As a result, these potential wind slabs likely won’t exist on every feature. So, you’ll need to constantly evaluate the terrain in front of you for signs of wind transported snow like textured surfaces and sharp drifts. Be leery of smooth pillow-like slabs especially if you’re traveling in high consequence areas. While you may find a few wind slabs near treeline, they will become more common as you head near the tops of the higher peaks around the Pass. Even though these slabs are now a couple of days old, the frigid temperatures may have allowed them to remain reactive. So, don’t write them off. You may still trigger shallow wind slabs, especially in rocky terrain.

    (2/18/2022)

    Example: Wind affected surfaces and cornices on Chair Pk shoulder. 

     

    https://nwac.us/public-obs/11451/

    Photo: Public Observation

Avalanche Discussion

We’re in for yet another frigid start to the day Thursday at Snoqualmie Pass. Once the skies start to clear, sunshine and warming temperatures should help conditions feel less arctic. Over the past few days, the snowpack has become rather aspect dependent. On sunny slopes, a thin breakable sun crust exists. This, combined with the very cold temperatures, should help limit any potential loose avalanche activity to a few very small isolated slides on steep southerly slopes. Below this surface crust, recent storm snow sits above a very strong spring-like snowpack. This melt-freeze layer is often the combination of the 2/19 and Valentine’s Day crust melded together. 

In shaded terrain, light dry unconsolidated snow continues to linger. Numerous observations from this past week indicate that around 16-20” of storm snow fell at mid and upper elevations, with considerably less at pass level. This mostly right-side-up snow buried a very thin crust (2/19). While the 2/19 layer can be tricky to find in some spots, you can often feel it a couple of inches above the more prominent Valentine’s Day crust. Between these two layers, weak snow grains have been reported, but have not produced any avalanches yet and fail inconsistently in snowpack tests. For the moment we’re keeping our eyes on these upper snowpack layers as we possibly head into a more active weather pattern beginning this weekend.

Regioni coperte