Lawinenlagebericht

East Slopes Central

Northwest Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 4 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

It's time to adjust our mindset and take a step or two back, because avalanche danger is increasing. Reactive conditions are expected to develop with new snow, wind transport, and warming temperatures on Sunday. Slab avalanches may be easy to trigger and large enough to be dangerous where wind has created thicker slabs at higher elevations. A powerful winter storm is expected to create a widespread natural avalanche cycle Sunday night through Monday. 

Lawinenprobleme

  • Wind Slabs

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

    New snow, rising temperatures, and strong wind will create reactive slab avalanches on Sunday. These could be large enough to bury and kill you at higher elevations near the crest where more new snow is expected to fall. Look and feel for instabilities as you travel and gain elevation. Plan to stick to lower angled slopes at higher elevations, and avoid wind-loaded pockets in sparsely treed terrain. There may be a brief lull in the storm during the day, but wind slabs may continue to be reactive. They're expected to form over very weak, sugary (faceted) snow surfaces, and may react in surprising ways. You could trigger stiffer wind slabs from the edges of, or from beneath steeper slopes. 

    At lower elevations, warming temperatures may create rollerballs and potential for small loose wet avalanches. Look for sticky wet snow and fresh, fan shaped avalanches as indicators of this type of avalanche. Avoid going underneath very steep, large mountain features if its raining or snowing heavily above you. 

    Example slab avalanche from the Baker Backcountry recently.

Avalanche Discussion

The upcoming set of storms will bring a drastic change to our snowpack over the next few days. For Sunday, up to 8" of new snow may fall near the crest, with less further east. During the day there's potential for a lull in the precipitation and winds ahead of the next, more powerful storm for Sunday night through Monday. With the rise in snow levels the snow could become thicker or moist at lower elevations during the day. Current snow surfaces are generally quite weak; Observers have documented a mix of facets and surface hoar over brittle suncrusts, wind stiffened snow, and soft recycled powder. With this in mind, conditions may become reactive in a hurry on Sunday, especially in areas with fresh wind drifts. The big test will come Sunday night into Monday when continued rising temperatures and heavy snow/rain may create a significant and widespread avalanche cycle.

There's anywhere from 1-3ft of lower density snow over a thicker crust from Valentines Day. There is less recent snow in the eastern half of the zone, so expect to find the older crusts near or at the surface in exposed, or lower elevation locations. On shaded aspects this crust is weaker and crumbly, on sunny slopes this crust is generally strong and thick. Higher elevation terrain features hold a fair amount of wind texturing, and older wind slab. Sunny slopes have thinner sun crusts, and may have surgery facets above and below. I made a trip to the North Fork of Fortune Creek in the Salmon la Sac on Wednesday, check out the observation for more information from that area. 

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