Lawinenlagebericht

West Slopes South

Northwest Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 5 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Stormy conditions dramatically changed the mountains this past week and finally built a real winter snowpack. Despite alluring soft powder, keep your eyes open for areas where the wind may drift the snow into slightly firmer slabs. Blowing snow and sharp cornices can highlight features you want to avoid.

Lawinenprobleme

  • Wind Slabs

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

    Several rounds of significant snow and strong ridgetop winds reshaped the mountain snowpack this past weekend. This trend should continue on Tuesday as more snow and moderate winds add to a developing wind slab problem. Due to the shifting nature of the winds along the Cascade Crest, you could encounter wind slabs on just about any aspect at mid and upper elevations. Avalanche professionals in the Crystal backcountry Monday found plenty of evidence of wind transported snow and drifts that cracked and failed along small slopes in exposed areas. As the snow and wind continue, these slabs could grow deeper. Look for clues like textured snow surfaces, drifts behind trees, and blowing snow to highlight features that could hold wind slabs. 

    With so much snow falling over the past several days, several storm interfaces and older wind layers exist in the snowpack. While we think most of the avalanche hazard should stem from newly forming wind slabs along exposed ridges, you might trigger a deeper avalanche in rocky or unsupported terrain. Make sure you feel confident in the snowpack before jumping onto these higher consequence slopes.

    (12/13/2021)

    Sharp cornices and smooth snow pillows indicate wind loading on this slope. East Peak, Crystal backcountry. 

    Photo: Robin Pendry

Avalanche Discussion

Nothing like a 5-day storm cycle to get the season going. Near constant snowfall, since 12/8 allowed the snowpacks to significantly grow by 3-5’ across the West South zone. Suddenly the mountains feel like winter. Unfortunately, this transition was accompanied by an avalanche fatality in the Crystal area (see below for details) on Saturday 12/11. Several natural and human triggered avalanches this weekend highlight the sudden change in snow conditions. While the recent storm snow is largely right-side-up, several storm interfaces can still be found. These layers should quickly gain strength as time moves forward. One layer we have our eye on is a thin crust (12/8) near the base of the snowpack. This layer sits about 4-6” above the late November curst or ground depending on your location. Some snow profiles found small faceted snow grains just above this curst. Inconsistent snowpack test results and its limited distribution across the landscape make this layer tricky to nail down and understand. If you dig in the snow, see if your snowpack tests fail suddenly or slide easily on weak snow near this crust. 

Despite all the new snow, we’re still dealing with an early-season snowpack that varies widely by aspect, elevation, and location. This leaves us with lots of questions and uncertainty. As the increased coverage allows you to venture into more areas, recognize that these unanswered questions could result in snowpacks and avalanches issues we are not aware of. Consider starting with smaller lower consequence slopes to gain information before stepping into larger terrain. 

Preliminary Report: On Saturday morning, December 11, a party of six backcountry tourers were traveling uphill in a closed section of the Crystal Mountain Ski Area known as Silver Basin. The party triggered a large avalanche on an NE to E facing slope at approximately 6600’. While all members of the party were initially caught, four were fully buried. A nearby party of two witnessed the event and immediately assisted in the rescue. Crystal Mountain Ski Patrol was also notified and responded to the scene. Unfortunately, one of the fully buried victims did not survive. NWAC and Crystal Mountain Ski Patrol will collaborate to conduct an investigation. Our deepest condolences to the family, friends, and community. 

SS-ASu-R3-D2.5-U; Crown Depth: estimated 2’ deep.

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