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

Very large deep slab avalanches have continued to release in upper elevation terrain, so think twice before going in or underneath big steep slopes while the snowpack adjusts to a heavy new load. Wind slabs may be triggered on a layer of buried surface hoar, steer around recently wind-loaded and unsupported slopes with dry snow. 

Avalanche problems

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3

    Very large, deep slab avalanches have released each day since last week, and Monday was no exception. The continued chances for more of these avalanches should determine where and how you travel on Tuesday. Avoid going in or underneath steep slopes, especially recently wind-loaded areas above 4,500ft. Cornices are big in some areas, avoid going underneath these because if they fall they could trigger very large avalanches. East to south to west aspects are the most concerning and have recently produced avalanches over 1,500ft wide. Slabs could be over 8 feet deep near the crest, and around 3ft deep further east in the range.

    A persistent weak layer involving facets on or sandwiched within crusts that were buried in mid-January has caused lingering instability for over a month. Avalanches have been documented on all aspects, and above 5,000ft. Unfortunately, this problem isn't going away. Activity may be slowly tapering, but each day we get reports of fresh avalanches with very wide and very deep crowns. Continue to tread carefully around and underneath places where these could run while the snowpack adjusts to the hefty amount of snowfall from last week.

    (3/1/2021) A very wide, very deep avalanche released from the east bowl of Chair Peak at some point between Sunday night and Monday morning. Photo: Bryce Hill

  • Wind Slabs

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

    Winds may create shallow slabs at upper elevations on Tuesday. Over the weekend, large wind slabs were triggered on a layer of buried surface hoar between 1ft and 2ft+ deep in Icicle Creek. This layer has been observed near Blewett Pass and near Mission Ridge as well. Avalanches may also be triggered outside of wind affected areas in the deeper storm snow near the crest. A sun crust from the middle of the week was responsible for a close call with a skier triggered avalanche in the adjacent Stevens Pass zone. If you trigger an avalanche in the upper foot or two of snow, it could be large or even step down to become a very deep and destructive avalanche. With wind slabs over buried surface hoar, and the potential for deep slab avalanches, you should avoid large avalanche starting zones, especially at mid and upper elevations. Avoid recently wind-loaded, leeward slopes 35 degrees and steeper.  Stick to lower angled and well-supported slopes and features.

    Example wind slab.

Avalanche Discussion

The following is a breakdown of the snowpack in the area: 

Upper snowpack: Southeast to southwest aspects will have a sun crust in the morning that may or may not soften during the daytime. Ski triggered (D2) avalanches occurred on north and northeast aspects in Icicle Creek at 5,400ft on Saturday. These were over 2ft deep x 200ft wide, and observed to have run on a layer of recently buried surface hoar. On Friday at Blewett Pass observers found a couple of layers of buried surface hoar stacked within wind slabs, 1ft and 2ft down, respectively. These were on both shaded and south facing aspects at about 5,800ft and produced clean, planer shears. A recent natural slab spotted on Saturday ran on a southeast aspect at around 5,600ft near Doctor Creek and looked about 1.5ft deep x 80ft wide.

Deeper down:

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.

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

2/26-27: 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. 

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. See the photo gallery below.

Regions covered