Bollettino valanghe

East Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Thu
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
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

You can trigger an avalanche in areas 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 wind slabs on leeward slopes at mid and upper elevations. Cold temperatures and continued drifting should 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. 

    (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.

Snotels sites across the East South have picked up 3-4 inches of new snow. You may find higher amounts closer to the Cascade Crest, and more specifically close to White Pass, that did fairly well with this last system. The main story was the radical wind speeds, with Sedge Ridge reporting gusts exceeding 60 mph out of the WNW during the early hours of day. These wind speeds velocities have likely created slabs in many unusual locations, such as further down slope than usual or well below treeline. So, keep an eye out for these at all elevations as you travel through the terrain. 

As we move out of this stormier regime the big question mark will be how the new load bonds with the old snow surface.  Leading up to this storm, observers have reported weak, faceting snow on northerly aspects.  So as new snow piles up, be sure to check how its bonding with the old snow interface. Use small test slopes or snowpack tests to gauge how easily the new snow fails. 

On Friday an observer in the American Ridge area reported finding good cold snow on east facing terrain, faceting snow in the shade,  and a sun crust on solar slopes that extended up to ridgetop.  At higher elevations they noticed winds drifting any remaining soft snow. Check out their full observation here. 

Let us know what you see by submitting a public observation. 

 

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