Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Recent snow fell on weak snow surfaces, and winds drifted new snow deeper in more exposed terrain. You can still easily trigger avalanches in steep terrain. These conditions will take time to heal, so keep your slope angles dialed down and travel in low consequence terrain.  Bitter cold temperatures will be another hazard to consider on Thursday.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Storm totals from December 20th varied throughout the zone, with some locations picking up over 1 ft of new snow and other locations further east picking up 6 inches or less. The strong, gusty winds were more consistent throughout the zone and drifted snow around even at lower elevations and in places typically more sheltered from winds. Wind and snow tapered by the end of the day on Tuesday. But the cold, dry snow easily drifted around, and you can expect to find a wide distribution of sensitive wind slabs. You may be able to trigger these slabs in unusual locations and on all aspects. Feel for harder snow layers over softer layers. If you observe long shooting cracks or find hollow sounding pillows of snow, you are traveling on or near a wind slab. You should identify these wind loaded areas and steer around steep terrain features where you find them. 

    We are just 48hrs out after a very stormy day, and very cold temperatures prevent much settlement of this new snow. So conservative terrain choices on lower angle slopes sheltered from the wind will be your best chance to avoid triggering or being caught in an avalanche.

    (12/20/2022)

    Remotely triggered wind slab near Blewett Pass on December 20th. 

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    In some locations, this new snow fell on weak, faceted crystals or surface hoar, and you may be able to trigger an avalanche in sheltered terrain where you find weak snow buried on 12/8 or even the most recent interface from 12/18. Observations came in on Wednesday from many areas in the mountains surrounding Leavenworth of touchy avalanche conditions, with slabs failing on weak snow on the 12/18 and 12/8 interfaces. These slabs may be buried up to 12-16inches deep and could propagate farther than you anticipate, or you could trigger them from lower angle slopes adjacent to steep terrain. Use quick hand pits to observe how well the new snow has bonded to the old snow surface. If the new snow easily slides off, you should dial down your terrain choices to lower angle slopes. You should avoid traveling on steep slopes if you observe recent avalanche activity, loud collapsing, or shooting cracks. Stability on the deeply buried weak faceted snow from mid-November (11/22) seems to be improving. The last known sign of instability involving this layer occurred last Thursday when whumping was observed east of Mission Ridge. While they may now be harder to trigger, they are also potentially larger. It may only take a large load or trigger to reawaken this deep instability. You should dig down to identify this weak snowpack structure and consider avoiding steep terrain where you find this setup. Be extra vigilant when traveling on northerly aspects with open slopes, particularly in the eastern portion of the zone.

    (12/21/2022)

    Intentionally skier triggered slide on Wednesday in Icicle Creek that failed on weak faceted snow at the 12/18 interface. 

    Photo: Nate Hough-Snee

Avalanche Discussion

If you take advantage of the brief break in the weather and venture out into new terrain, be aware that conditions may still be touchy in certain terrain. In some locations, you may still be able to trigger lingering storm slabs where over a foot of new snow rests on weak, sugary faceted snow. In other areas, you could find a more favorable snowpack setup. After a storm, it is always important to observe how well the new snow bonds to the old snow surface. Jumping, skiing, or snowmobiling over small, steep test slopes is a great way to see if the new snow will slide easily. You may also trigger fast-moving dry loose avalanches in steep terrain. While these typically start small, they can become larger as they move downhill and can easily knock you off your feet in consequential terrain. 

Thursday is shaping up to be the coldest day of the season. So make sure to prepare for these unusually cold temperatures with extra warm layers, face shields, and ensure those grip heaters are up and running.

Many locations in the East Central zone have a weak snowpack structure with facets formed in mid-November buried near the ground. Most avalanches on these basal facets were on 12/8 and 12/9 and observed from north and east aspects in wind-loaded terrain near Mission Ridge. One very wide avalanche was observed on the 14th in the East North zone near Twisp (see photo below). Further west, observations indicate that the snowpack is deeper, and the weak layers are stronger in the Teanaway and the Salmon La Sac areas.

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