Bulletin d’avalanche

East Slopes North

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 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

A beautiful day is in store, and loose dry avalanches may run from steep, rocky and sunny slopes. In wind affected terrain, slabs should continue to be reactive and may surprise you as they rest over weak, sugary snow. Stick to well supported and lower angle slopes, especially if you observe signs of instability like shooting cracks or the snow feels slabby or hollow.

Problèmes avalancheux

  • Wind Slabs

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

    Snow has been drifting readily since Wednesday when a cold NE wind arrived. Snow surfaces likely consisted of sharp, faceted grains and now you might find areas of harder, wind packed snow. Be careful of reactive wind slabs, as instability may linger longer than expected through Friday. If you find fresh drifts that create shooting cracks when provoked, steer around pillows and drifts on steep slopes. 

    Look for wind rippled and stiffer snow surfaces, these will help pinpoint where you could trigger avalanches.  Areas near ridgelines or pronounced ribs may be especially prone to drifting. Slopes beneath large cliffs also tend to harbor slabs, as loose snow spindrifts off and accumulates below. You can use small test slopes to check how easily the snow fractures. You can also choose slopes less than 30 degrees or look for wind-sheltered terrain to avoid this problem.

    Example windslab avalanche that ran on the 1/31 crust from last week. Copper Creek, SE, 7200ft

    Photo: Harry Keane

  • Loose Dry

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

    With the low density new snow, sluffs may run naturally with direct sun, or could be triggered by a person on a steep slope. These shouldn't pack too much punch, but the larger the terrain feature the more destructive they could become. Look for other point releases, and feel for moistening snow surfaces on steep south facing slopes. Avoid hanging out beneath large steep or cliffy features during the 'heat of the day' while the new snow settles out.

    A natural solar triggered loose dry avalanche from a previous season. Photo: Josh Hirshberg

Avalanche Discussion

The zone picked up anywhere from 3-6" of new, very low density snow on Thursday. Observers had been reporting small ski triggered wind slab avalanches from alpine terrain every day for a handful of days, and Thursday was no different. An observer found multiple shallow (2-6") natural wind slabs near McCleod Mtn. 

At mid and upper elevations, observers have been finding up to 1.5ft of recent snow over a stout crust from January 31. Lower elevations hold substantially less new snow over this crust, so travel may be more difficult and slippery in some areas. A layer of faceted snow rests above the crust from January 31st, and may have been the culprit for this small pocket avalanche triggered by a party while skinning up Kangaroo.

Snowpack information is limited outside of the Highway 20 corridor, including Harts Pass, the Chelan Sawtooths, and near and east of Mazama. If you get out into the backcountry, let us know what you find!

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