Bollettino valanghe

East Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto last year. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

There will be plenty of new snow to be carried around by the wind on Thursday. Coupled with some afternoon sun breaks, it could be a dynamic day in the backcountry. Look for red flags that new snow is unstable such as long shooting cracks from your equipment, audible collapsing, and recent natural or triggered slab avalanches. If you see small bits of snow rolling down on a sunny slope, a small wet snow avalanche could soon follow.

Problemi valanghivi

  • Wind Slabs

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

    Both new and old slabs are on the table for Thursday. A large triggered slab will be running on a slick crust below. Smaller slabs could be running on mid-storm layers that took shape during the system. With moderate to strong winds forecasted, we expect most hazard to be relegated to wind-affected terrain, but be on the lookout for signs of storm slab instability in sheltered terrain.

    Wind slabs typically form just below ridgelines and on exposed convexities and gullies. Blowing snow, cornices, and fresh drifts will be the most helpful visual clues to look for.  Expect to find wind-transported snow on either side of any given ridgeline where you find these features. Pay attention to the feel of the snow underneath your equipment as well; a change to denser or uneven snow indicates the wind influenced that spot. Signs of storm slab instability are the same: cracking, collapsing, and recent slab avalanches.

    (3/12/2025)

    A small wind slab intentionally triggered on the north facing side of a ridgeline in the East Central zone.

    Photo: Payton Schiff

  • Loose Wet

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

    The sun will poke through in the afternoon and rapidly influence new snow. While we expect moderate to strong winds will largely hold off a lot of warming, you can't bank on it this late into the year when the sun is high in the sky. The typical initiation of wet loose avalanches involves rollerballs and pinwheels or chunks of snow falling from cliffs and trees. If you're on a sunny slope and the snow is becoming sticky and moist, find lower angle or shadier slopes.

    (3/21/2021)

    Wet loose avalanches often initiate where snow sheds off rocks and trees onto the slope below. Note that there are both small rollerballs and wet loose avalanches in this image. 

    Photo: Zack McGill - Cascade Mtn Ascents

Avalanche Discussion

Diverging a bit from the norm, this storm system will impact the zone from east to west and likely deposit an equal amount of snow throughout. It's already impacting the zone Wednesday evening and will largely conclude by 9 am Thursday morning. Areas near the Cascade Crest may continue to see small showers throughout the day. Due to the nature of this storm, there could be big differences in the kind of precipitation particles falling - such as graupel for a period of time - which could create mid-storm layers. The wind will not subside with the snow. Expect to encounter blustery ridgelines and continued wind transport throughout the daylight hours. 

On Wednesday, Avalanche professionals reported reactive wind slabs in the nearby East Central zone. Many of these slabs were sliding on a crust that formed earlier in the month. This crust was also recently observed by an NWAC Forecaster traveling in this zone last weekend. Without much of a reprieve before this next system, we expect similarly elevated avalanche hazard for the East South.

There is not enough consistent snow coverage below 4500 ft for there to be much avalanche hazard, but newly exposed rocks and stumps due to previous snowmelt might be obscured by fresh snow, so keep an eye out. A small wet loose avalanche could knock you over and carry you over hazards like these.

Submit an observation to help NWAC Forecasters reduce uncertainty. It can be short, simple, and even anonymous. Visit the Recent Observations page to get an idea of what backcountry travelers share that helps entertain the forecasts in other zones.

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