Bollettino valanghe

Stevens Pass

Northwest Avalanche Center
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Pericolo valanghe

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

Your main concern is wind drifted features at higher elevations, where you might find deposits up to a foot thick that formed out of the few inches we've received since Saturday night. In areas where you identify these deeper drifts, steer around them on steep slopes, especially if they span large areas or if you encounter cracking snow as you move across the slope. All but north-facing aspects received a fair bit of sun on Sunday, and are now crusty, making travel challenging on these aspects at all elevations. 

Problemi valanghivi

  • Wind Slabs

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

    The Stevens Pass Zone received a couple inches of snow Monday, and may receive a couple more by Tuesday. Small drifts which already formed at upper elevations may continue to grow larger with the additional snow and winds which are actively shifting new snow.  You're most likely to find drifted areas on the leeward slopes near ridges, in gullies, and around rocky outcroppings. On Monday I found drifts up to 8 inches deep in the Stevens Pass zone at around 5000ft. They easily cracked as I stepped along them, although they had only formed along the ridge itself. If the drifts span further downslope and could pick up more mass if they slide, I would be more concerned, especially in higher consequence terrain. 

    Search for signs of wind loading by feeling for heavier, thicker snow beneath you. Visually hunt for clues such as textured or featured snow surfaces and actively blowing snow. Don't ignore obvious signs such as cracking. If you encounter thicker drifts, especially if the thicker snow coats a large expanse of the slope, or shows weakness such as cracking, steer around the slope if it is greater than 35 degrees. You're more likely to find wind slabs most reactive at exposed higher elevations, but they could reach down into near treeline elevations as well. 

    (4/18/2022) Moderate winds were actively loading old and new snow midday Monday. This tiny wind lip was about 8" deep, and little chunks were cracking and running from the small feature. They were not concerning here, but applied to higher elevations and with more snow and wind they could break larger. Photo: Irene Henninger

Avalanche Discussion

East, south and west aspects saw plenty of sunlight on Sunday, and are now coated with a crust. In some areas, the few inches of new snow may cling to the crust, but where I traveled on Monday, in a more exposed area, wind was quickly transporting the new snow and the surface was still a crust. The crust is challenging to travel over, as the smooth surface were slippery. Meanwhile, steeper surfaces were textured with rollerballs and wet loose avalanche debris- not the most pleasant snow to move over. Additionally, the crust could make an excellent sliding surface for any wind drifted pockets that deposit on the crust. 

On Monday I dug 2 pits in the Stevens Pass Zone, one on a northerly aspect and one on south-facing terrain. It was no surprise that the south-facing slope had a thick crust on the surface, and there were several crusts down to the 4/8 layer. We're not expecting to see avalanches in the layers above the 4/8 crust, as the surface is locked down with the new (4/18 crust). On the north the snowpack is very different - I mainly found right-side up, well consolidated layers, aside from one hard-to-detect crust about 6 inches from the surface, probably having formed from greenhousing last week. In other areas I've recently dug throughout the zone, I've seen graupel layers and there may be other shallowly buried weaker layers, and I wouldn't completely rule out avalanches stepping down to old snow layers above the 4/8 crust. 

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