Lawinenlagebericht

East Slopes North

Northwest Avalanche Center
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Lawinengefahr

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

Warming temperatures and very strong winds will create dangerous avalanche conditions on Sunday. Wind slabs, storm slabs, and loose wet avalanches may begin to occur by the end of the day. Take a big step back, and only go into the backcountry if you can confidently avoid avalanche terrain while a strong, warm storm begins to affect the area.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Very Likely
    Größe
    1–2

    Very strong westerly ridgeline winds will continue to transport snow onto lee slopes. You'll find firmer wind-affected snow near and above treeline and even on open slopes below treeline.  Shooting cracks or hollow-sounding snow are signs you could trigger an avalanche on similar nearby slopes.  Avoid open slopes steeper than 35 degrees anywhere you find freshly drifted snow, sticking to lower angle or wind-sheltered terrain. Cornices may begin to fail and trigger avalanches in alpine terrain on Sunday as well.

    Example of active wind drifting snow. Notice the fracture near the edge of the wind lip, indicating touchy conditions.

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    5-10" of snow is expected with a significant rise in temperatures through Sunday. Storm slabs may become easily triggered and could run naturally in areas that get on the high end of that amount. These won't' be your recent light and fluffy slabs, they may be thick and dense. Very strong winds may create thicker and more reactive slabs in any exposed, open slopes. You could trigger storm slabs from distance, and they could step down to deeper layers. Steer around avalanche terrain if finding signs of instability such as shooting cracks and recent avalanches. 

    Example storm slab avalanche.

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    At lower elevations, loose wet avalanches may begin to run naturally by the afternoon. These could grow to become large on steep slopes. Wet slides have the potential to run over common hiking trails and snowmobile trails in the zone below 4,000ft. Stay off of, and out from underneath any steep slopes if you notice rolleballs, or fan shaped avalanches.

    Example wet loose avalanche that ran over a hiking trail.

Avalanche Discussion

A big change is coming with the arrival of an atmospheric river on Sunday. Rising temperatures and very strong winds will be accompanied by steady snow and rain. Sunday night into Monday a significant dump of heavy, wet snow is expected. Observers noted intense wind transport on Saturday, and we expect that to continue for the next few days. The Methow picked up between 6" and 10" of snow by Friday morning, and observers noted natural, loose dry avalanches below steep rock features in the alpine. 

Persistent slab avalanches are still on our minds in outlying parts of the zone west of Washington Pass and more recently in the eastern mountains. On Wednesday 2/17, an observation from the Twisp River drainage in the near treeline band found the mid-January facet/crust combo unreactive in snowpack tests and over 3 ft down.  Buried surface hoar slightly closer to the surface,  less than 3' or 80 cm down, showed sudden results in snowpack tests. No new or recent avalanches down to this layer or other signs of instability like whumpfing, or collapsing were noted.  Further west, the last persistent slab avalanche occurred near Rainy Pass on Feb 8th (see photo below). It is suspected to have run on the mid-January crust-facet layer about 2-3ft below the snow surface. This layer may begin to 'wake up' over the next couple of days.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources. Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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