Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

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

In sintesi

You may not get many warnings as we're a number of days post-storm, and obvious signs of instability are waning, but large, wide, and surprising avalanches remain possible. Winds have transported snow into slabs on a variety of slopes, so besides large scary persistent slabs you could trigger smaller, shallow wind slabs. Expect another very cold day, but at least the sun should make an appearance. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    Large and widely breaking slabs remain possible to trigger. These avalanches can propagate widely around terrain features, and you may be able to trigger them from a distance. Look for weak snow buried above and/or below a crust from December. This structure is widespread throughout the zone and in many parts of the region. A layer of buried surface hoar from January 2 sits an inch or two above a crust from December 30th. This has produced the most widespread instability and avalanches in the Teanaway, Salmon la Sac and surrounding areas. Mission Ridge also reported widely propagating avalanches on older faceted grains above a crust last week. 

    The best way to manage this avalanche problem is to avoid steep open terrain and slopes connected to steep terrain above. Instead, seek out low-angle, simple terrain. Before this storm, there were close calls with avalanches on these persistent weak layers. These same layers are buried much deeper and are expected to continue to be a problem for the near future. 

    (1/10/2024)

    Backcountry travelers near Lake Wenatchee remotely triggered this avalanche from a low angle adjacent slope. This avalanche ran on weak, facted snow over the Solstice Crust.

    Photo: Pat Riffie

  • Wind Slabs

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

    East winds picked up on Saturday and drifted the very low density snow into shallow slabs at all elevations. Strong winds from the west also built slabs on Thursday, and these may now be hidden or obscured. Feel for wind stiffened snow as you travel, and use visual clues as well as you can to identify wind loaded or recently wind loaded terrain features. Avoid steep slopes where you expect to find these stiff, wind-drifted slabs, especially if finding signs of instability like shooting cracks or hear whumphing collapses. Any small slab near the surface could step down and become a much deeper, wider, and potentially unsurvivable slide. 

    (12/30/2022)

    Example of long shooting cracks in a fresh wind slab. These long cracks are bullseye information of unstable snow.

    Photo: Rob Pollard

Avalanche Discussion

Saturday was the coldest day of the season so far and it could be the rest of it.  Temps hit -20 at Blewett Pass, -18 at Mission Ridge and Dirtyface, and -12 in downtown Leavenworth...Brrr!  Some hardy souls went into the mountains to experience this arctic blast, and reported increasing winds during the afternoon. Tracks that had been set in the morning became sifted in as the easterly winds picked up. If you go out, be sure to bring extra layers to combat cold injuries and the potential for a minor accident to turn into a serious one. 

Over 3ft of snow has fallen in most areas of East Central this week, with around 1.5ft in the easternmost portion of the zone. NWAC forecasters went to the lower slopes of Cashmere on Saturday and found small faceted grains over a crust above 3,000ft. This is the classic weak structure that can result in a persistent slab avalanche. Another NWAC forecaster visited the Salmon La Sac area on Wednesday. At 4600ft, she found around 70cm of new snow with a thin melt-freeze crust from a brief warmup midstorm buried 45cm down. This new melt-freeze crust showed potential for propagation in a snowpack test. Weak snow beneath the Solstice Crust also showed propagation in these test results. 

If you get out, let us know what you see by submitting a public observation!

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