Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Look for deeper new snow and signs of recent wind drifting as you gain elevation. The greatest danger will be in wind-loaded terrain but loose snow avalanches should also be on your radar. There are still plenty of early-season hazards that can increase the consequences of a fall or small avalanche. 

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Steady winds and snowfall are the setup for slab avalanches on wind-loaded slopes. There were no observations from above 5000' on Thursday to verify conditions, but wind slabs are probably the most hazardous avalanche problem you will encounter traveling across high ridgelines or in exposed terrain. Active loading should taper off by midday, so look for clues like scoured snow surfaces and thicker drifts to identify where denser, deeper, easier-to-trigger slabs reside. 

    Loose dry avalanches are also possible in steep terrain. Look for larger, longer-running sluffs where the crust is frozen, firm and smooth below the new snow. Small sluffs can be consequential with thin snowpack conditions or terrain traps in the runout.

    One upside of big rain events is they create a crust that's easy to identify below any new snow that follows. As you gain elevation and change aspects, use a ski pole or just dig down with your hand to track changes in snow depth above the crust.  More snow? Greater chances of finding a slab or triggering a sluff.

    Dense, cracking, textured snow is a telltale sign of wind slab.

    Photo: Robert Hahn

Avalanche Discussion

Wet avalanche activity is likely finished as temperatures fall. It’s still wise to avoid spending time below waterfalls, rock faces, and brushy cliffs holding snow. Small glide avalanches and rockfall can initiate from these features even after temperatures drop below freezing.

Friday is the first day forecast to have halfway decent visibility. Some might be inclined to head to higher elevations where there is more dry snow and less crust. If you are one of these folks be aware there have been no observations from the alpine since the weekend. Prepare to make your own avalanche and snowpack assessments as you could find conditions different than forecast.

Weather stations recorded 0.4-0.8” of precipitation on Thursday. Heather Meadows at 4200’ saw 6” of new snow. It’s safe to assume there is 8” or more at upper elevations or on wind-loaded slopes. Expect an additional 4-ish inches by Friday morning. Temperatures are falling along with the new snow, so look for light density, right-side-up new snow layers - except for wind-loaded areas.

Below the most recent snow, there's 1-3’ around Heather Meadows. A profile on Dec 5th showed a thoroughly rain-affected snowpack with alternating layers of melt forms and moist rounds. The weak layer responsible for Saturday’s avalanche activity (link, link) was not found. Lower elevation and many mid-elevation locations have minimal snow and difficult travel. 

Regioni coperte