Bollettino valanghe

East Slopes South

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

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

In sintesi

Before jumping into exposed, downwind terrain, investigate the snowpack for signs of wind-loading. Unstable, wind-affected snow is often more consolidated and will crack or collapse underneath your equipment. Choose a lower angle or more sheltered slope if you encounter signs of instability.

Problemi valanghivi

  • Wind Slabs

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

    Wind slabs are more sensitive closer to the Cascade Crest where more new snow fell recently. Wind-loaded terrain is most often found just below ridgelines and in cross-loaded gullies. You probably won't see blowing snow so look for clues that indicate previous snow transport such as cornices, soft pillow-like slabs, or denser, uneven snow surfaces. Read on in the forecast discussion if you're unsure how to understand uneven snow surfaces. Step off the skin or sled track to test small, low-angle slopes representative of the slope you plan to ski or sled before committing to steep terrain. While you're at it, stick your hands in the snow and check the bond of the slab sitting over the crust formed on 01/10. If you encounter cracking or collapsing, stick to slopes less than 35 degrees or find more sheltered terrain.

    (1/7/2025)

    Small rider-triggered wind slabs in the Superbowl. 

    (6800, ENE)

    Photo: Payton Schiff

Avalanche Discussion

An NWAC Forecaster traveled to Ahtanum Meadows on Sunday to investigate the persistent slab problem we had listed throughout last week. He continued to find widespread buried surface hoar around 12in/30cm deep on many aspects but he did not get concerning results in snowpit tests on this layer. He also noted that numerous steep slopes had been tested by riders and that no triggered avalanches were evident. As we move into a period of calm, dry weather, we expect the snowpack to only continue stabilizing. With that being said, keep in mind that buried surface hoar is still in the snowpack and we only have limited info from a small area within the zone. You could still find an isolated pocket of instability. If your risk tolerance is such that you do not feel comfortable high marking or sledding on steep slopes knowing that there is weak snowpack structure, you can just default to lower angle terrain.

If you do plan to recreate on steep terrain, you can reduce your risk by choosing slopes that are more planar and free of convexities and terrain traps. Make like a forecaster and dig around on many aspects to look for weak layers and unstable test results. If you get out in the coming days, we'd love to hear if you still found buried surface hoar or reactivity in the snowpack. Public observations are essential for NWAC forecasters to build more informed forecasts. Please help us reduce uncertainty by submitting an observation.

If you've been reading on because you want to find out which direction you should look for wind loading if you encounter rippled, uneven snow surfaces, here's the best way I have found to think about: the "pointed" ridges of the ripples "point" towards the prevailing wind direction. It is a similar concept to how riming on trees usually happens on the side of the tree facing the wind. Keep scrolling for some photos that show examples of this.

Especially on slopes that see direct sunshine, you may encounter surface snow that is warming and weakening. Snow shedding off cliffs/trees and rollerballs/pinwheels indicate that the snowpack is losing cohesion and beginning to move. If you begin punching deeply through the snowpack and the snow feels heavy and sticky, consider moving to shadier slopes.

Help NWAC Forecasters reduce uncertainty by submitting an observation!

Regioni coperte