Lawinenlagebericht

East Slopes Central

Northwest Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

Unpredictable and unsurvivable avalanches up to 8ft deep remain possible, as do fresh wind slabs and cornices. Continue to make conservative terrain choices, avoiding going on, or underneath steep slopes while the snowpack settles. Significant, and destructive avalanche events have been occurring naturally in this zone, and nearby zones following last weeks heavy snowfall. 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    3

    The uncertainty and unpredictability of deep and persistent slab avalanches should determine where and how you travel. Avoid going into or underneath steep slopes. Avoid traveling on and beneath slopes 35 degrees and steeper. Slopes 5,000ft and higher and on east to south to southwest aspects are the most concern and have recently produced avalanches over 1,500ft wide and up to 6 feet deep. We know that terrain in Icicle Creek has been especially unstable with these from observations on Saturday.

    A persistent weak layer involving facets on or within a crust that was buried in mid-January has plagued the snowpack with lingering instability for over a month and a half. South and East aspects appear to be especially problematic, but we know persistent slabs have also run on north and northwest aspects. Unfortunately, this problem isn't going away for a little while, and we shouldn't be surprised to hear about more of these monsters in the coming days. Continue to tread carefully around these sleeping dragons on Sunday.

    (2/24/2021) Very large avalanche reported from a South aspect at 5,500ft near Manastash Ridge on the 24th. This instability will continue to be a problem in the near future.

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    2

    Fresh snow and strong winds will again create reactive wind slabs. Even outside of wind affected areas, you could trigger avalanches in the recent storm snow near the crest. A layer of surface hoar has been found 1-2+ feet down near Blewett Pass and in the Icicle, and was responsible for ski triggered avalanches on Saturday. A sun crust from the middle of the week was responsible for a close call with a skier triggered avalanche at Stevens Pass. 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, storm slabs, and the potential for deep slab avalanches, you should avoid large avalanche paths, especially at mid and upper elevations. Avoid wind-loaded, leeward slopes 35 degrees and steeper.  Below treeline, stick to wind-sheltered slopes and well-supported features. 

    In the eastern edge of the zone, the strong late February sun may again create wet loose avalanches on Sunday. If the sun is out where you are, expect these to happen on steep slopes that face toward the sun during the middle of the day. Moist, sticky snow and rollerballs are good indicators that the snow is capable of producing these. Time your travels to avoid steep south facing slopes in the middle of the day to avoid getting avalanched by a wet loose slide.

    Example wind slab.

Avalanche Discussion

Ski triggered (D1.5 and D2) avalanches occurred on north and east 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 surface hoar. Very recent, much deeper natural avalanches appeared to run Friday on the mid-January layer in the terrain around Victoria Lake in the Icicle. Another recent natural looked about 1.5ft deep x 80ft wide from a southeast aspect at around 5,400ft near Doctor Creek. On Friday at Blewett Pass I found a couple of these 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 very large avalanche occurred on the 24th that appeared to have slide on our mid-January crust from Manastash Ridge, and snowpack tests on Friday near Blewett Pass showed that people can still trigger avalanches on it. A thin melt freeze crust from the 22nd can be found about a foot down at elevations up to 5,000ft in the zone, though snow has been bonding well to this.

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, wide, and destructive avalanches ran on, or around the 22nd:

Dirty Face Mtn- both the SE and E faces produced avalanches to at least D3, running far down the mountain with some very deep crowns.

Round mtn- avalanches on SE aspect as well as a D3 avalanche on SW near 5,000ft on Nason Ridge to the west of Round Mtn.

Tumwater Canyon-  Avalanches ran on NE-SE with numerous loose wet to size D1-2 and a few slab avalanches to D2.5. 

In the Icicle drainage:

Sixty-six Hundred Ridge- An avalanche on NE, 6600ft ran size D3, R4 and took out trees

Big Slide creek- A SE aspect above treeline. Size D3.5-4

Mt Cashmere- Above the Eight-mile trailhead.  7,000ft, SSE. D3.5-4

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