Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Winds and new snow have created another set of slabs in higher, exposed terrain. Storm snow instabilities still need more time to settle out, even outside of wind affected terrain. Look for shooting cracks and recent avalanches, and steer around steep or consequential slopes if you suspect instabilities. 

Problemi valanghivi

  • Storm Slabs

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

    Chances remain to trigger slabs both at the interface of new and old snow, and within new snow layers. Some potential for buried surface hoar exists, and persistent slabs have become a problem in the adjacent East Central zone. Look for long shooting cracks as you travel, and check for planar failures with a variety of tests. Sparsely treed terrain that faces north and east may be the most likely areas to find this instability. 

    (1/9/2023)

    Small, shallow storm slab beneath a rock outcrop.

    Photo: Willie Webster

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2

    You can trigger shallow wind slab avalanches on leeward sides of ridges. Pay attention to drifting patterns and textured surfaces. You can avoid these avalanches by sticking to wind-sheltered terrain, low-angled slopes, and steering around wind pillows and drifts. If you see cracks shooting through the snow or stiffer surfaces where the snow slides easily, move to slopes less than 30 degrees. Winds have shifted between easterly and westerly directions, so you could find reactive slabs on all aspects.

    (1/5/2023)

    A triggered small (D1) avalanche on the leeward side of a ridge in Liberty Bowl, next to South Early Winter Spire. SW, 7,450ft.

    Photo: NWAC Public obs

Avalanche Discussion

Willie reported two small soft slab avalanches hit the closed Hwy 20 in the Liberty Bell group on Monday morning. Winds were strong with intense blowing snow in the morning, then skies broke and the wind calmed down. Shallow storm slabs were easily triggered about 8" down. Tests showed potential for failure down about 1ft and 1.5ft on large, preserved stellars.

It was an active weekend in the eastern Cascades. On Sunday, a party reported triggering a small slab near Varden Creek on a north aspect at 6,000ft. The skier that triggered the slide was the fourth on the slope, and got carried a little ways but was luckily ok.  WSDOT forecasters reported a wet avalanche that gouged to the ground near the town of Methow. On Saturday, an observer near Twisp reported a mix of snow and rain with a similar avalanche gouging to the ground. Another observer near Washington Pass reported cracking near treeline. On Friday, Willie Webster went to the  Blue Lake trailhead and reported light to moderate blowing snow and a few small wind slab and loose dry avalanches from the past week.   On Thursday, observers in Liberty Bowl triggered a small slab avalanche in an area of wind-drifted snow on a leeward side of a ridge near South Early Winters Spire. The crown was 50ft wind and it ran 500 vertical feet. 

A cycle of very large avalanches occurred December 24-27th near Washingotn Pass involving older weak layers that were buried in late November and early December. Near the pass, the weak layers are now capped with a stout crust and melt-forms from the Christmas rain event.

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