Bollettino valanghe

East Slopes Central

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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In sintesi

Recent new snow and increasing wind speeds will build reactive slabs of wind-drifted snow. Steer around steep slopes that are being actively loaded or show signs of recent loading. If you find yourself traveling in the eastern edges of the zone, keep an eye out for dry loose avalanches running in steep terrain. 

 

Problemi valanghivi

  • Wind Slabs

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

    East winds have already been at work drifting new snow onto unusual aspects and terrain features. Look for these wind-drifted slabs forming on west facing aspects or cross-loading slopes. 

    Recent new snow and heavy drifting have created slabs 1-3 ft thick at mid and upper elevations. Cold temperatures and continued drifting  will help keep these slabs fresh and sensitive to your weight on Thursday. You’ll find these slabs forming on the leeward side of ridges, under cornices, in chutes/couloirs, and cross-loading alpine features. 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.

    (12/14/2022)

    Blowing snow is a great way to identify possible wind loaded slopes. 

    Photo: Willie Webster

  • Loose Dry

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

    Cold temperatures will help keep the new snow low density, so keep an eye out for dry loose avalanches (also known as sluffs) on steep terrain features at mid and lower elevations. Expect these loose avalanches to be easily triggered on any steep slopes. 

    Pay attention to steep terrain features and consider the run out or parties below you. These slides will be on the smaller side, however they can still be consequential if paired with a terrain trap or people traveling under you. So have a plan before skiing into steeper features and make sure the run-out is clean. 

     

    (2/21/2023)

    You may encounter small dry loose avalanches in steep terrain, especially if you travel in the Wenatchee's. 

    Photo: Lee Lazzara

Avalanche Discussion

Well, the Wenatchee Mountains got crushed with Mission Ridge over-producing and receiving  17 inches (.24 swe) of low density new snow. In this part of the zone observers reported blower riding conditions, but also a fair amount of wind-transport from East winds. The Mission Ridge Pro-Patrol reported triggering dry loose avalanches during mitigation work. 

NWAC observer Brooke Maushund traveled further west near Lake Wenatchee and found 5-6 inches of new snow sitting on the 2/13 crust. She reported east winds actively drifting new snow into isolated reactive pockets. 

These next few days are going to be down-right cold as a cold upper trough parks over the western US. So be prepared with extra warm layers and consider the consequence of something going wrong during frigid temperatures like this. 

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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