Bollettino valanghe

East Slopes North

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
Open full map
Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

It may be another beautiful day before clouds increase in the afternoon. Unfortunately, the recent wind drifted snow into stiff slabs at mid and upper elevations where you could trigger an avalanche. Choose lower-angle terrain where you see deep drifts or textured surfaces, and steer clear of steep slopes below corniced ridges.

Problemi valanghivi

  • Wind Slabs

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

    Shifting wind directions formed stiff wind slabs on various aspects at mid and upper elevations. For the past few days, there have been consistent reports of small skier-triggered and natural wind slabs from the Washington Pass area. Before the new snow and increasing winds, snow surfaces may have harbored weak, faceted grains. These weak layers can often make wind slab instabilities last longer than usual. If you find fresh drifts that produce shooting cracks, steer around pillows and drifts on steep slopes. Look for actively drifting snow, formations around trees and rocks, or stiffer snow surfaces to help you identify where you could trigger a wind slab avalanche. 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. However, with inconsistent distribution of these weak layers, these tests could be misleading. You can avoid the problem by sticking to well-supported or lower-angle slopes and seeking wind-sheltered terrain for travel. Cornices are large, and you should avoid lingering underneath these monsters. They are a hazard just on their own but can also act as a large trigger and initiate an avalanche as they fall on the slope below. 

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

    Photo: Harry Keane

Avalanche Discussion

A clear morning will give way to increasing clouds throughout Saturday and a slight temperature bump, but nothing we would consider "warm". Expect steady winds that may not be impressive in speed but could still drift the recent low-density snow around. The sun is growing stronger this time of the year, so if it's sunny later into the afternoon, it could start to affect snow surfaces more substantially. With the low density of the new snow, sluffs may run naturally with direct sun, or a person could trigger one on a steep slope.

On Thursday, the zone picked up anywhere from 3-6" of new, very low-density snow. Observers are reporting small ski-triggered and natural wind slab avalanches in alpine terrain every day for a handful of days, and that pattern continued on Friday. Professionals noted multiple small pockets of wind slabs that released naturally at upper elevations. 

At mid and upper elevations, there is 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 challenging and slippery in some areas. A layer of faceted snow rests above the crust from January 31, and may have been the culprit for the prolonged period of instability in wind-affected terrain. 

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!

Regioni coperte