Bollettino valanghe

East Slopes South

Northwest Avalanche Center
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Pericolo valanghe

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

In sintesi

Wind loaded slopes are where it's feasible to trigger both small and large avalanches, but small avalanches are more probable. Consider navigating around slopes steeper than 30 degrees where you find pillow-like drifts and cornice development, particularly on aspects and elevations that harbor a weaker snowpack. You can further reduce your risk by choosing short, planar slopes free of hazards and terrain traps.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Winds have been blowing from the east for the last few days. They will shift back to a more typical westerly direction on Friday and increase in speed in the afternoon. With low density snow available for transport throughout the week, don't be surprised if you find wind affected snow on various aspects and lower down on slopes than normal. Fresh slabs will be small but have the ability to knock you off your feet and carry you over hazards such as rocks and cliffs. There is a smaller chance of triggering an older slab large enough to bury you; you will most likely find these slabs on north and west facing aspects at upper elevations.

    Wind-loaded snow is often found just below ridgelines and in cross-loaded gullies. Red flags are cracks shooting out from your skis or sled and recent slab avalanches in similar terrain. Visual clues such as cornice development, rippled snow surfaces, and blowing snow that will be visible throughout the day will help direct you to the side of a ridgeline where wind-loaded snow may be lurking. 

    Although fairly unlikely, a triggered wind slab could "step down" and become a more treacherous persistent slab avalanche on newly wind-loaded slopes, just like this avalanche observed in the nearby East South zone. Read below for more details.

    (2/12/2025)

    Shooting cracks in fresh 6-8" thick wind slabs at the Pass on Wednesday. These were more than 1000' below ridge line. Shooting cracks are an obvious sign of instability and mean you should avoid steep wind-loaded slopes. 

    Photo: Josh Lipkowitz

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1.5–2

    The likelihood of triggering a potentially fatal avalanche is low but not impossible. This zone hasn't had much activity or signs of instability on weak snow layers associated with the January Drought Layer (JDL) this week. However, the distribution is nearly impossible to pin down, and there is no new on-the-ground data to know for sure one way or another. What we do know is that poor snowpack structure exists in many areas, and shifty wind may have made downwind terrain more perilous on various aspects. 

    This particular persistent slab problem has been even more tricky to manage than your average uncertain persistent slab problem. You may or may not see clear signs of instability - cracking, collapsing, or recent slab avalanches - telling you to back off before it's too late. Use the clues laid out in the wind slab problem to help you identify wind-loaded slopes, understanding that a small wind slab avalanche can "step down" and trigger a deadlier persistent slab avalanche. You can reduce your risk by choosing slopes that are shorter, more planar, and free of hazardous cliffs or terrain traps. When in doubt, default to lower angle, sheltered terrain.

    (2/3/2025)

    A skier triggered persistent slab avalanche near White Pass. This slide released over a 100ft wide and 2-3ft deep. WNW, 5600ft SS-ASu-D2-R2-O

Avalanche Discussion

A Valentine's poem to summarize:

Roses are red, violets are blue, steer around wind loaded slopes so you don't lose your boo.

Cracking and collapsing are red flags, and so is blowing snow, low angle sheltered terrain will be a safer place to go.

You'll want to be home for Valentine's dinner, but buried weak layers still exist, choose more simple terrain to reduce your risk.

Our fingers, toes, and hearts will finally get the chance to defrost on Valentine's Day, as Friday marks the end of frigid temperatures and dangerous wind chill factors. That being said, Friday will still be a rather windy day, especially in the afternoon. If you plan to get out with your Valentine or Galentine, be sure to still pack layers.

The likelihood of triggering a large persistent slab avalanche is decreasing, but the unique nature of this particular persistent slab problem has many long time avalanche professionals still traveling conservatively. An NWAC forecaster traveling in the northern end of the zone on February 7th found poor snowpack structure and propagating snowpack test results. More recently, an observer just over the border in the West South zone reported whumpfing. This problem has been hard to pin down due to the high variability of snowpack surfaces leading up to new snowfall at the end of January and little data for this zone. Additionally, sustained cold weather has slowed down the healing process for the JDL. Stack the odds in your favor by choosing well-supported terrain and enjoying high-quality powder riding in more sheltered terrain.

Submit an observation to help NWAC Forecasters reduce uncertainty. It can be short, simple, and even anonymous. Any information you have will help us write more accurate forecasts that will, in turn, better help guide your backcountry decision making.

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