Lawinenlagebericht

West Slopes Central

Northwest Avalanche Center
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Lawinengefahr

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

Kernpunkte

Stormy conditions will make for challenging travel in exposed terrain. Look out for and avoid fresh, sensitive slabs of new and wind drifted snow. Reduce the risk of triggering an avalanche by sticking to lower angle, sheltered terrain. 

Lawinenprobleme

  • Storm Slabs

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

    A storm overnight into Sunday will drop 1' or more of new snow across West Central with greater amounts farther north in the zone. In addition to fresh storm slab layers, expect strong winds to transport snow and build thicker slabs on leeward slopes. Last week a layer of facets and surface hoar developed at the snow surface in neighboring zones and was likely present in West Central as well. Strong winds on Saturday disturbed or destroyed these weak grains in most wind exposed terrain, but they could still exist in sheltered areas and produce avalanches when loaded with new snow. Natural and human triggered storm slabs are more likely during periods of intense snowfall and rising snow levels.

    Track the new snow depth as you gain elevation and especially as you transition into more wind affected terrain. Investigate the bond of new wind and storm slab layers as you travel. Don’t ignore obvious signs of instability like shooting cracks, whumphs, or recent avalanche activity. Approach any steep slope with caution and remain aware of terrain above you. If snow levels creep up during the day expect to see wet avalanche activity at low elevations.

     

     

     

    Example of storm slab avalanche. Note the cracks above the crown where the slope was a little too low angle for the slab to slide.

Avalanche Discussion

A big change is underway in the North Cascades this weekend with a decent storm Sunday and then a warm, wet atmospheric river setting up early Monday. A glorious week of high pressure, cool temperatures, and good snow conditions is coming to a fitting end with a major reset in the next 24-48 hours.

Observation notes:

- Wind transport early Saturday was spotty with some terrain features seeing moderate transport while others saw little despite strong winds. This is likely due to sun crust on windward slopes locking in the snow and preventing transport. More transport was observed on the highest peaks where less crust formed in the last week.

- Strong winds stirred up the snow surface and dispersed faceted snow and surface hoar that formed during high pressure. That being said, wind affected surfaces still held the weak grains but the layer lacked continuity. In some protected start zones the surface layer was unaffected.

- The upper snowpack above the late-January crusts is not “weak” per se but is also not the bulletproof snowpack we often have prior to a storm. Suspect layering below breakable crust on south aspects, small facets around crusts buried February 14th and 19th and other layer interfaces are notable in snowpit observations. While testing shows these layers are not really interfaces we are worried about triggering, smaller storm and wind slab avalanches could step-down into these layers and produce very large avalanches.

- Dry snow above the late-January crusts could produce wet avalanches if snow levels end up being a bit higher with the atmospheric river event and rain falls near and above treeline.

 

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