Bollettino valanghe

East Slopes Central

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 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You can still trigger a slab avalanche in recently wind-transported snow near and above treeline. Your danger will be greatest in areas picking up fresh snow on Monday. Look for textured snow surfaces and firm, punchy layers to identify and steer around areas suspect for wind loading.

Problemi valanghivi

  • Wind Slabs

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

    The southeast portion of the East Central zone (around Sasse Ridge) picked up 6-8" of snow on Saturday (0.6" SWE) with rising temperatures leading to denser, stickier snow above cold lower-density snow. While this is may not be enough snow to form a storm slab, increasing ridgeline winds through Tuesday will continue load some of this denser snow into avalanche start zones and these shallow slabs will remain reactive on Tuesday. Identify and navigate around denser pillows where this denser snow has piled up in the lee of ridgelines or beneath sharp, fresh cornices.

    More ubiquitously distributed throughout the zone, older wind slabs formed during the larger storm on December 18th may be stubborn to trigger but could be large. The size of these avalanches warrants heightened caution around open terrain features, especially near ridges at upper elevations. These slabs may feel stiff or hollow as you punch a pole through a firm layer - a good sign to seek safer, lower-angle terrain. Use your pole, probe, or hand pits to identify areas of stiff snow over soft snow and observe how easily the stiff upper snow slides on the underlying surface. Navigate around wind-loaded slopes steeper than 35 degrees.

    (12/19/2021)

    A crown from an avalanche (size D2.5) that ran on 12/18 in storm snow. Above treeline, NW, Chiwaukum range

    Photo: Matt Primomo

Avalanche Discussion

Milder temperatures Monday night and Tuesday add an element of uncertainty to the forecast as a strong cold air pool increasingly gives way to warmer air trying to spill over the Cascades from the west.  Below and near treeline elevations in the southern and western portions of the zone seem most likely to experience warming. However, cloud cover and a low December sun may limit the impact to the snow surfaces. If you find that the snow becomes sticky and wet or you observe rollerballs, you can trigger small loose wet avalanches on slopes steeper than 35 degrees. These kinds of avalanches may be particularly hazardous given the early season snowpack and near terrain traps such as creeks or gullies. 

A significant storm and natural avalanche cycle on Saturday followed a a relatively benign day on Sunday, with cold temperatures and even clear skies in many areas. The mellow weather allowed for 3-4” settlement in the new storm snow from December 18th. In southern parts of the zone you will find up to 6-8" of denser snow deposited 12/20 on top of the lower density cold snow. In northern portions of the zone, full sunshine may have produced rollerball activity or formed a zipper crust on south-facing slopes.

We have limited data from elevations above treeline and in the northern portion of the zone. In some areas, weak snow may exist above crusts, creating the potential for larger avalanches, so approach complex or large terrain cautiously. Use snowpack tests to determine how well bonded the overlying snow is to these crusts.

There is a lot of variability throughout the zone, and a more substantial snowpack exists in the western portions. Winds have built slabs on lee aspects even in the eastern parts of the zone that lack a substantial snowpack. Expect the avalanche danger to differ throughout the zone, and stability on one slope may not represent adjacent slopes. 

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