Bollettino valanghe

East Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The most dangerous places will be in areas that hold wind-drifted snow resting over weak, faceted grains about 1 ft below the snow surface. As you travel, look for blowing snow and textured pillows to help you identify problematic slopes. Dial it back if you notice shooting cracks, hear whumphs, or feel stiff, hollow-sounding snow. 

Problemi valanghivi

  • Wind Slabs

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

    Wind slabs will stay fresh and reactive to your weight on Saturday. Increasing south and east winds will continue to drift snow into cohesive slabs. Due to recent east winds, don't be surprised if you find these slabs all over the compass on Saturday. Look for these slabs as you change aspects, especially in areas that promote drifting, such as the downwind sides of ridges, beneath rock and cliff bands, or on the breakover of unsupported features. 

    Numerous observations have illustrated weak snow grains sitting over a crust about 6 inches- 1.5 ft below the surface. These grains have been responsible for recent human-triggered avalanches in the east-central and west-south zones. If a wind slab rests over this structure, the resulting avalanche could break widely. To avoid this problem, stick to more sheltered slopes and avoid travel on terrain steeper than 35 degrees if the surface snow appears wind textured and drifted. Take a big step back if you notice shooting cracks or hear whumphs. 

     

    (11/21/2023)

    Blowing snow like this can help you identify what slopes are loading up. 

    Photo: Matt Primomo

Avalanche Discussion

An incoming system will bring a strong dose of east winds along with increasing chances for precipitation as the day progresses.Unfortunately, this system will be more of a strong wind event than a snow event for the east-south mountains. 

The recent storm on 2/15 deposited 10-12 inches of low density new snow across the zone. In much of the region, this new snow now sits over a weak snowpack just above the early February crust. Observers regions-wide, including in an NWAC forecaster in the Darland Mt area on Thursday, are finding weak, junky snow just above the stout EFC crust. This weak snow has already produced avalanches in neighboring zones ( observation here).

In most places, this new snow lacks the slab-like characteristics to produce an avalanche. However, you’ll likely encounter this slab in wind loaded terrain. These slabs may not be that big, but could be large enough to ruin your day if they fail on well developed facets over a crust. 

To make matters worse, we’re in the midst of a significant east wind event. There's an old adage, ‘Nothing good comes out of east winds,’ which also stands true in my experience. These east winds will often surprise people since slabs will form in not-so-common terrain such as west aspects or across terrain features (cross-loading). 

Expect very thin (or even non-existent) snowpacks at lower elevations and on some steep southerly slopes. Unfortunately, we're still talking about travel hazards. Slick crusts, exposed obstacles, open creeks, and bare ground continue to make travel more adventurous. While this storm was a welcome refresh, it's probably still best to use established roads and groomed trails for better access to the high country. 

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