Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Shifting winds over the last week have formed wind slabs on various aspects at mid and upper elevations.  Continue to use caution on steeper slopes near ridgelines, chutes, and near the base of cliffs where you're more likely to encounter stiffer wind-textured snow.  

Problemi valanghivi

  • Wind Slabs

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

    There's been a consistent trickle of observations reporting stiffer wind slabs and long shooting cracks on a variety of aspects from the Washington Pass area over the last few days.  While older wind slabs should be more difficult to trigger with each passing day, a weak faceted snow layer underneath recently formed wind slabs has allowed this problem to stick around. 

    If you see long shooting cracks in firmer wind-textured snow or signs of recent avalanches, avoid nearby steep slopes.  Slopes beneath large cliffs also tend to harbor slabs, as loose snow spindrifts off and accumulates below.  You can always pivot to well-supported or lower-angle slopes and seek out wind-sheltered terrain for travel. 

    Cornices are large, and you should avoid lingering underneath these behemoths. They are a hazard in their own right but cornice failure can also trigger consequential avalanches on slopes below. 

    Relatively warmer temperatures along with a fair amount of cloud cover should make loose dry avalanches less likely on Monday.  You'll still want to keep an eye out in wind-sheltered and very steep northerly terrain where you find loose surface snow and it's easy to produce sluffing on test slopes. These avalanches would likely be small but could be problematic around terrain traps.  

    A wind slab avalanche ran on the 1/31 crust last week (2/9). Copper Creek, SE, 7200ft

    Photo: Harry Keane

Avalanche Discussion

Winds have moved around but have largely been out of the north from Wednesday through much of Sunday and have been accompanied by colder temperatures (single digits to teens) and periods of light snow.  Temperatures popped into the mid-20s in the Washington Pass area on Sunday as the winds shifted to WSW allowing milder air into the region.  This shift to a slightly milder regime looks likely to stick around even as ridgeline winds back and increase out of the S-SE through Monday afternoon.

Observers have reported generally small skier-triggered and natural wind slab avalanches at predominately upper elevations stretching back into the middle of last week.  Sunny weather on Friday formed a thin sun crust on southerly aspects at mid and lower elevations.  On shady slopes, at mid and upper elevations, there is up to 1.5ft of recent snow over a stout crust from January 31st. Lower elevations hold substantially less new snow over this crust, so travel may be challenging and slippery in some areas. A layer of faceted snow rests above the crust from January 31st, and may be the culprit for the prolonged instability in wind-affected terrain. 

Snowpack information is limited outside of the Highway 20 corridor, including Harts Pass, the Chelan Sawtooths, and near and east of Mazama. If you get out into the backcountry, let us know what you find!

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