Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Tue
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You could still encounter some lingering storm snow related problems on Monday. You can look for heavy snow over weak snow or blocks failing easily in your tests as you travel to help you identify potential slabs to manage. Buried weak snow has produced surprising avalanches in adjacent zones recently and could be waiting for the right time to rear its ugly head at the Pass.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2.5

    The recent storm snow consolidated into a more cohesive slab in many areas on Sunday. Using uptrack tests, hand shears, or small test slopes while you travel can give you clues about the likelihood of a slab failing and how deep a potential avalanche could be. Bullseye information such as recent avalanches, shooting cracks, or whumpfing collapses should drive you into more conservative terrain. Be leery of steeper slopes, convex rollovers, or wind-loaded pockets where triggering an avalanche could be more likely. 

    Additionally, the presence of weak grains at the base of the recent storm snow could produce surprising avalanches in some areas. If you are unlucky and trigger an avalanche on this layer, it could break above you or wrap around terrain features. You can take a look in the snow for a thin gray line or feather-like snow grains at the depth where you see blocks failing easily in your tests to help identify this tricky problem. When in doubt, stick to terrain under 35 degrees with plenty of natural anchors.

    (12/9/2022)

    This skier triggered avalanche occurred Friday 12/9 in the Alpental Valley. N-NE, ~4000ft. SS-AS-D1-R1-U

Avalanche Discussion

We are a day removed from a decently large storm that dropped multiple feet of snow around the Snoqualmie Pass zone. Fluctuating temperatures, periods of gusty winds, some mixed precipitation, and a bit of blue sky have helped to transition the snowpack from light and fluffy to more consolidated and heavy in many areas of the zone. On open slopes near treeline, a thin surface crust was reported on Sunday. Additionally, the warm temperatures helped snow shed from trees and rocks, creating small debris piles in some instances. We are still lacking observations from the highest elevations, but you could find more wind-loaded areas or deeper and drier snow as you ascend. 

We have been talking about the 12/8 buried surface hoar throughout much of the region and this weekend, NWAC forecasters confirmed its existence in the Snoqualmie Pass zone. Although this layer has shown up in snowpack tests, it has not shown a propensity to propagate and there are no known avalanches on this layer at the Pass. However, on Friday, three skier-triggered avalanches in the Alpental Valley appear to have broken at a depth that appears to match the 12/8. In the neighboring West South zone, there was a skier-triggered avalanche at White Pass that is believed to have failed on the 12/8 surface hoar and a natural avalanche at Mount Rainier that appears to have failed on this layer as well. You can check out the West South forecast for more information on some of the unusual activity we've been seeing in that zone.

Even though the hazard rating has dropped, that doesn’t mean it should be open season out there. You may want to consider traveling and selecting terrain more in line with how you would at Considerable danger: making careful snowpack evaluations, and using conservative decision-making. And if you see an avalanche or dig in the snow, let us know what you find by submitting an observation.

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