Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
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

A repetitive pattern of light snow, clouds, and shifting wind directions continues to build shallow slabs of wind-drifted snow. Most avalanches may be small in shallow fresh drifts, but there is potential to trigger a large avalanche that breaks 2-3ft deep in older wind drifts. Reduce your uncertainty by steering around steep slopes with stiff wind-textured snow. 

Problemi valanghivi

  • Wind Slabs

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

    Over the last few days, there's been a consistent trickle of observations reporting stiffer wind slabs and long shooting cracks on various aspects from the Washington Pass area. 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. The shifting wind patterns also make it difficult to predict where wind slabs formed in the terrain. So, look for them on various aspects or even mid-slope. Consider the high consequences of triggering a wind slab that breaks wider and deeper than expected if it fails on weak snow above a stout crust from January 31st. Avoid nearby steep slopes if you see long shooting cracks in firmer wind-textured snow or signs of recent avalanches. Slopes beneath large cliffs also tend to harbor slabs, as loose snow spindrifts off and accumulates below. You can always pivot to well-supported and lower-angle slopes or seek wind-sheltered terrain for travel. Cornices are large, and warmer temperatures on Tuesday could make them more prone to failure. 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.

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

    Photo: Harry Keane

Avalanche Discussion

Tuesday will again feature your regularly scheduled weather pattern with cloudy skies, light snow, and easterly winds. The only noteworthy difference is slightly warmer temperatures, so you could see some small wet loose avalanches or rollerballs below 4000ft. 

Notable information from the entire Washington Cascade range and from nearly every forecast zone is that since February 15th, 13 unintentionally human-triggered avalanches have failed on or just above the stout crust from the end of January or Early February. Most of these avalanches have been between 5000ft and 8000ft and cover all aspects. Thankfully, no one was injured in these incidents, but this is critical information that this weak structure is out there and capable of producing avalanches. The distribution is uncertain, but you could get unlucky. It may be best to stick to sheltered terrain or low-angle, well-supported slopes while the weather keeps giving us windy conditions along with dribs and drabs of snow. 

Observers have generally reported small skier-triggered and natural wind slab avalanches stretching back into the middle of last week, primarily from upper elevations. 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 and Harts Pass. Let us know what you find if you get out into the backcountry!

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