Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

A warm day with clearing skies will bring wet avalanches to sunny slopes. It may be easy to trigger avalanches in the recent snow, especially where overnight winds form drifts at upper elevations. Give yourself plenty of safer terrain options, and be ready to stick to lower-angle and sun-sheltered slopes.

Avalanche problems

  • Wind Slabs

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

    Strong westerly winds will form fresh slabs overnight and should taper off by daytime on Tuesday. Watch for natural avalanches, cracking in the snow, and small test slopes that slide easily as indicators of instability.  While you may not see actively blowing snow, pay close attention to recent wind drifting patterns. Avoid steep leeward, wind-loaded slopes. Above treeline, avalanches could be bigger and easier to trigger. While unlikely, a similar wind event last week resulted in a couple of very large, natural avalanches above treeline (see photo and Discussion below).

    (3/11/2023)

    Crown of a very large avalanche in the Icicle Creek Drainage. We have a lot of uncertainty surrounding this avalanche problem. But best to make conservative choices in alpine terrain.

    Photo: Matt Primomo

  • Loose Wet

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

    Wet avalanches could occur naturally as the snow surface becomes moist. After a cloudy start, clearing will allow the sun to warm the snow surface. Watch for roller balls and snow falling from trees as indicators that the snow is getting moist and weak. Moist snow surfaces and wet snow that slides easily are also good indicators that you could trigger an avalanche. Watch for natural avalanches coming from overhead slopes and hazards like falling tree bombs and cornices. You'll want to exercise caution near terrain traps like above cliff bands or tight gullies where a slide could push you into hazards. 

    (3/13/2023)

    Debris from a very large natural avalanche that occurred 3/13 in Tumwater Canyon, between Fall ck and Cabin ck.

    Photo: Matt Primomo

Avalanche Discussion

Storm totals on Monday showed a large spread with the most snow falling in the northwest portion of the zone near Trinity and Holden (nearly 1ft with 0.9" of water). Weather stations in the Salmon la Sac area picked 6-8" and the Wenatchee Mountains received 2". The stormy weather and poor visibility prevented extensive observations. A very large, natural avalanche ran in Tumwater Canyon between Cabin ck and Fall ck (see photo above).The recent snow is piling up over a couple of intermittent sun crusts and a pair of rain crusts from Valentine's Day, which can be found 3-5ft deep. We suspect the recent very large avalanches may have run on these crusts in the Icicle Drainage and Rock Mountain. We don't have much info yet on the extent of this problem, but as the stormy weather persists, so could the potential for these very large avalanches. The most suspect terrain is wind-loaded northern aspects above 6000ft. The Valentine's crust often presents as a crust/facet/crust sandwich, with weaker snow beneath the upper crust. Observations indicate wide variability in the structure and depth of this layer throughout the zone. Leading up to these avalanches, observers noted isolated signs of instabilities on this layer in the Icicle drainage and the eastern Highway 2 Corridor. 

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