Bulletin d’avalanche

West Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

Sat
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

A weak storm will bring light snowfall and moderate winds overnight into Friday morning. Look for and avoid fresh slabs of wind drifted snow that form in steep, downwind terrain. Periods of sun could warm up southerly slopes and produce wet avalanches - keep track of terrain overhead if the sun comes out.

Problèmes avalancheux

  • Wind Slabs

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

    Additional snowfall and just strong enough winds overnight could build another batch of fresh wind slabs. They will likely be small but some could be larger. All could take an unwary traveler for a ride. Wind-loaded slopes can be identified by the usual signs like scoured ridgelines, fresh cornices, and other wind-drifted features that point to where slabs may have formed. Active loading should back off mid-day.

    Test slopes and hand pits can help you monitor differences in layering as you change aspects and gain elevation. Evaluate the bond of wind slabs as you go and don't rush into steep terrain - or just find a lower-angled line around steep wind loaded areas.

     

     

    (2/8/2023)

    Snowmobile triggered wind slab avalanche at Schriebers Meadow. East aspect @ 6000'.

    Photo: NWAC Public Obs

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    Warm temps and a bit of rain initiated a cycle of loose wet avalanches farther north Thursday and the same is suspected of happening in West Central. Low elevations likely saw wet avalanches triggered by rainfall but mid and upper elevations hold drier snow. Bursts of sun between periods of overcast could warm up snow that escaped the rain today.

    Keep track of the amount of sun poking in through the clouds and get ready to change course if it warms up. Look for signs of instability like pinwheels or rollerballs as telltale signs of warming. If sun breaks are minimal, you may see no signs of instability or avalanches.

    Small wet loose avalanches triggered by snow shedding from trees and rocks.

    Photo: Julz Holder - Grounding Truth

Avalanche Discussion

Avalanche conditions differ across the various frontiers of West Central. Areas east and south have seen avalanche activity taper with storm and wind slabs becoming less reactive. Stevens and Snoqualmie Pass did not see much precipitation Thursday but did see some small wet avalanches triggered by the sun. More large natural avalanches occurring during the storm were reported but overall avalanche danger is on the decline.

It's a much different story to the north in a number of ways. Rain to about 5000' triggered a round of wet avalanches in the Baker Backcountry/West North and probably other areas as well. Snow levels were about 1000' higher than anticipated. Numerous human triggered avalanches were reported Wednesday. Most were smaller in size (D1) and triggered on steep, convex features - typical locations to trigger such avalanches after a storm. 

More noteworthy were three different human triggered avalanches reported from Canyon Creek and also Schriebers Meadow (click for observation) on the south side of Baker. These avalanches were large, surprising, and quite dangerous.  One was triggered from low on the slope. They are not typical wind slabs but they occurred in obviously wind loaded terrain. No injuries were reported but in one of the avalanches the rider was buried with only their hand exposed at the surface and promptly dug out. 

No avalanches like these were reported anywhere else on the west slopes. But there is a lot of big, alpine terrain in West Central that could hold a similar snowpack - in this case, a layer of facets and thin melt-freeze crust buried anywhere from 1-4' deep. If you end up going big in the coming days keep an extra dose of caution in the top lid of your pack. Consider triggering one of these avalanches as not impossible until proven otherwise.

 

 

 

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