Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Winds have generally been light, but so is the new snow. Look to identify areas that may hold shallow wind slabs with new and old snow before entering steep slopes. If you experience loud collapses or cracking, theres a deeper weak layer at play, so stick to lower-angle slopes.

Problemi valanghivi

  • Wind Slabs

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

    Keep an eye out for "red flag" warning signs like shooting cracks or whumphing collapses as you gain elevation and enter wind-exposed terrain. Check for punchy, softer layers below stiffer snow. Steer around thicker pillows of drifted snow on steep slopes. If you find any of these clues, move to lower-angled slopes, windward terrain, or lower elevations.  While these slabs are likely becoming less reactive, consider the consequences before entering very steep or unsupported terrain.

    Less likely, but very dangerous, would be triggering older, deeper slabs that rest on facets in the lower half of the snowpack. While this structure may be isolated, forecasters are still finding it, and Josh was surprised by a large collapse around 7,600ft on a southwest aspect on Saturday.

    (12/3/2022)

    Very shallow 2-3" chunks of wind slabs could be initiated on kickturns above treeline. Hairpin valley, SW, 7,500ft.

    Photo: Josh Hirshberg

Avalanche Discussion

About 3" of new snow fell at Washington Pass on Thursday. This covered up a mixed bag of surfaces including crusts on steep south slopes, firm wind board, and soft snow. Prior to Thursday, wurface hoar was observed to be large in many places, and was fairly widespread. While it may have been blown over by wind, its likely preserved just under the surface of wind-sheltered slopes.

Earlier in the week, observers in the Hairpin valley reported that westerly winds formed slabs and stiffened snow surfaces on Tuesday into Wednesday. While unlikely, avalanches aren't impossible on steep open terrain at low elevations, near valley bottoms, or east of about Mazama where the snowpack remains shallow. Josh visited Goat Peak just north of Mazama on Monday. Snowpack tests were easy and impressively reactive with propagation where he found older drifted slabs. He, and a separete party in the area reported collapses in open terrain below treeline and one at as high as 6750ft. Cold temperatures and shallow snow have kept the snowpack weak in the eastern mountains.

You can find facets from mid-November (buried 11/22) just below the middle of the snowpack on most slopes from Washington Pass into the eastern mountains. It's uncertain if they remain intact as far west as Rainy Pass. We haven't received reports of avalanches on this layer, but it's been the source of numerous reports of collapsing, mostly at lower elevations. The grains appear to be bigger and "sharper" further east. Near and west of Washington Pass and below about 7,000ft the facets received rain and you'll find them just beneath a crumbly crust. The overlying snowpack also varies from west to east with elevation. It's generally deeper as you move west and higher in elevation. Overall, the weak layer seems most problematic where the grains are the biggest, closer to the surface, and have a stiffer slab immediately on top. Big storms could create avalanches on this layer.

The winter is off to a great start. We're still gathering baseline snowpack information for much of the zone, so be ready to make your own assessments of the snow and avalanche conditions. Let us know what you see by submitting observations.

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