Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Thu
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

You can trigger an avalanche in spots where the wind has drifted new snow into reactive slabs. Once you lose the wind, you lose the problem. So consider traveling on more sheltered slopes and give steep wind-loaded features some space.

Problemi valanghivi

  • Wind Slabs

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

    New snow and heavy drifting have created slabs 1-2 ft thick at mid and upper elevations. Additional new snowfall, cold temperatures, and continued drifting will help keep these slabs fresh and sensitive to your weight. You’ll find these slabs forming on the leeward side of ridges, under cornices, in gullies/couloirs, and cross-loading alpine features. Don’t be surprised if you find these wind-drifted slabs further down slope than usual due to recent strong winds. 

    As you travel use visual clues to help you identify slopes of concern. Look for blowing snow, cornice growth, ripples, or rounded pillows at the snow surface to identify where the wind has been at work. If you see shooting cracks under your skis/sled or feel wind-stiffened snow, be ready to take a big step back and avoid nearby steep slopes. 

    This problem is dangerous alone, but any triggered wind slab at upper elevations has the distinct possibility of stepping down and breaking on deeper buried weak layers sitting on a slick crust. If this does occur, the resulting avalanche could be surprisingly large. Create extra space between your route and potential runout zones from complex, upper elevation alpine terrain.

     

    (1/17/2023)

    Shooting crack in wind drifted snow - a red flag that should not be ignored.  Avoid wind loaded slopes if you notice signs like this. 

    Photo: Joe Dellaporta

Avalanche Discussion

Avalanche Fatality: Colchuck Pk, East Central Zone: Read the preliminary report here.

If you find yourself traveling in the Wenatchee Mountains, you may notice a few extra inches of low density snow. Wind speeds should relax, but switch more easterly, which may start drifting new snow onto unusual aspects like west-facing slopes. 

The East Central weather stations have recorded anywhere from 3-7 inches of new snow on Tuesday. The main story was the radical wind speeds with Mission ridge reporting over 100 mph gusts out of the southwest. These high wind speeds have likely built wind slabs in many unusual spots, such mid-slope features or even well below treeline. The Mission Ridge Pro Patrol went out for a round of control work and found wind slabs to be stubborn and generally well-bonded to the old snow surface. 

On Friday observers reported natural, large wind slab activity from alpine terrain near Holden Village. Both in the Salmon la Sac and eastern Highway 2 corridor, we've found the crust from the 13th to be fairly thin and breakable, with weaker snow beneath it. This structure a concern as the storm continues. We may see avalanches break above and below it, and could see slides run on even deeper weak layers. A crust from MLK weekend has been problematic for deeper slab releases in zones to the west. Some large and very large avalanches with wide propagation occurred from the 8 through the 13th in the Stevens Pass and Snoqualmie zones. This storm may act as a good test for this layer.

If you get out into the mountains, let us know what you see by submitting a public observation. 

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