Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Variable, weak, and slick old snow surfaces exist, and triggering avalanches in new and wind drifted snow is possible. A firm sun crust may make avalanches on steep southern aspects more likely. If small test slopes produce small slabs or shooting cracks, you should steer around steep terrain. 

Problemi valanghivi

  • Storm Slabs

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

    Another storm is forecasted to favor the eastern slopes of the Cascades on Saturday. A few inches of new snow recently buried various weak surfaces and slick crusts. These weak interfaces could have survived in some locations, and this storm may add 8 to 10 inches of additional snow over these interfaces. This complicated setup leads to uncertainty regarding how well new snow will bond with the old surfaces, and adjacent slopes with slightly different aspects may have variable stability. Observations from South facing aspects near Lake Wenatchee indicated a very weak interface with new snow sliding easily on the underlying melt-freeze crust formed during clear sunny weather over New Year's weekend. Be particularly cautious in these southern aspects, where you may easily trigger avalanches that run far on this slick crust. Quick hand pits are a great way to investigate the new snow interface. Steer around steep slopes where new snow slides easily, or steep test slopes produce small slabs. Avalanches will be larger and more dangerous in areas where the wind has drifted snow into deep pillow-like drifts. Steer around these stiff, hollow-sounding pillows in steep terrain. 

    (12/20/2022)

    Small steep test slopes like this are great for testing out how well new snow bonds to old surfaces. 

    Photo: Public Observation

Avalanche Discussion

Observations from Blewett Pass and Mission Ridge on Thursday and Wedge Mountain on Friday were of 3-5 inches of new snow that was largely unreactive even in wind loaded areas. However, very different conditions existed on South-facing aspects near Lake Wenatchee, where new snow slid easily and ran far on the underlying melt-freeze crust.  This variable and potentially weak interface (1/4/23) from Wednesday night's storm will be one to watch with this next round of snow in the forecast for tomorrow. 

Other surfaces that may be buried by Saturday's storm and contribute to the complicated snowpack are below.

-Wind stiffened snow in exposed terrain near ridges at upper elevations.-Sun crusts on southern aspects.-Rain or Freezing fog melt-freeze crusts at lower elevations.-Weak, faceted snow and surface hoar in sheltered northern locations.

As you travel, use quick hand pits and small test slopes to observe how well the new snow bonds to underlying surfaces. In very steep terrain, loose dry avalanches may run far and fast on these slick crusts. Be aware if you are traveling underneath cliffs, gullies, or in extreme terrain where small avalanches can have increased consequences.

Regioni coperte