Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

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

The chance for very large and unsurvivable avalanches will maintain dangerous avalanche conditions. Warming temperatures and sun could set off wet avalanches or even large cornice fall. Continue to avoid traveling on or under large open slopes, steep sparsely treed terrain, and areas that received recent wind drifting.

Avalanche problems

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3

    Very large, natural avalanches have occurred as recently as Sunday or Monday with more recent avalanches in other zones. Deep persistent avalanches can destroy cars and houses and occur with no warning. An avalanche would be unsurvivable if you were caught while recreating on foot or on a snow machine. Even avalanche professionals with decades of experience have trouble predicting these avalanches and accurately make decisions about them. Wednesday's warm temperatures and sun will add another layer of uncertainty to this equation.

    The way to stay safe is simple: Avoid traveling in or under large avalanche paths. Avoid leeward slopes 35 degrees and steeper where the wind drifted slabs in the past week. Use extra caution on any steep slope, even around sparse trees. Before you commit to traveling in avalanche terrain, ask yourself, "What's the largest avalanche that this slope can produce, am I willing to take that risk, and is there a safer option?"

    (3/2/2021) Aerial photo of a recent and very large natural avalanche in the Benchmark/Fortune Mountain just over the border into the West Central Zone. Photo: George Coiner

  • Wind Slabs

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

    There are two main concerns around wind drifted snow:

    1) Large cornice falls triggered by warming temperatures and sun on leeward sides of ridges. Falling cornices the size of vehicles could easily injure you if you're on or under them. They could also trigger very large deep slab avalanches. We suspect this may have happened in a few recently observed avalanches. Stay out from under and well away from cornices. If you're traveling on a ridge, clues like exposed rocks and vegetation can tell you where you can stand without being on an overhung cornice.

    2) Small slabs may have formed at the highest elevations with west and southwest wind since Monday. While they'll be small, you could trigger these wind slabs on steep, leeward slopes. This adds to older wind slabs which are now difficult to trigger. Any wind-loaded terrain is suspect for more dangerous deep persistent slabs. You may find isolated areas where older slabs could be triggered on surface hoar that was buried on the 25th.

    An example a recently wind loaded slopes and cornices.

  • Loose Wet

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

    Another day of warm temperatures and sun could be enough to see wet avalanches on slopes that have yet to slide in the past couple of days. If slopes are getting soft and wet, move to lower-angle and more shaded terrain. These avalanches are normally easy to manage. With the complexity of dangerous conditions on Wednesday, it's best to stay off of slopes prone to these avalanches.

    (3/1/2021) Small point releases originating from rocks near the Bomber Chutes, just outside of the Mission Ridge ski area boundary at 6,200ft on an E aspect. These likely ran on Feb 27th or 28th. Photo: Josh Hirshberg

Avalanche Discussion

Recent notable avalanches:

3/1: WSDOT avalanche teams observed a recent (within the past 24hrs) natural D3.5 deep slab from high, north facing terrain in the Chiwaukum Range. They also triggered an 8ft deep D3 in southeast facing terrain at around 6,000ft off Rock Mountain east of Stevens Pass (the remaining hangfire in West Camp path). Chair Peak at Snoqualmie Pass ran as a D3.5 at some point between Sunday night and Monday morning with a crown 10-15'+ deep. On observer reported numerous very large avalanches near Fortune Peak, just west of this zone.

2/28: A fairly fresh-looking deep persistent slab avalanche from upper elevation terrain was spotted in the Chiwawa drainage. 

2/26-27: A natural D4 avalanche released from Rock Mtn and came just short of Highway 2. A couple of D2.5-3's terrain in Icicle Creek (see photo below).

2/24: A deep persistent slab occurred on a south aspect near Manastash Ridge. 

Since the weekend, the weather has been relatively quiet with intermittent sun, warm temperatures and occasional westerly wind. Despite the calm weather, the snowpack has been slow to adjust to the major load from the prior week. Feb 25-26th brought a storm with near to 2" of water equivalent at the Cascade Crest and extreme winds. This came on the heals of an even bigger storm. From the 20-23rd a massive storm brought up to 6" of water equivalent to the mountains near the crest but much less to the Wenatchee Range further east. Numerous deep and very wide avalanches (Many D3-3.5's, some size D4's)  ran on, or around the 22nd in the mountains near the crest, and some deeper slabs were reported from the Wenatchee Range. Similar avalanches have continued into this week. While conditions may be less dangerous in parts of the Wenatchee Mountains, due to less recent snow, the same weak layers can be found and recent avalanches have been triggered on them. See the photo gallery below.

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