Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Fri
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

Anticipate a transition day as temperatures drop and light rain turns to snow. Avoid slopes holding freshly wind-drifted snow if traveling at mid and upper elevations. Steer clear of areas below snowy cliffs and steep terrain with running water that can still shed snow or rocks.

Update @ 7:30am:  Danger rating at mid-elevations raised to Moderate with greater snowfall than expected. 

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    New snow combined with moderate to strong wind will build fresh slabs. Look for and avoid wind slabs in places where you observe new snow and active or recent wind transport. Use test slopes and hand pits to see how well new slabs are bonded to the layers below, especially where they form over a frozen crust.

    Observations are minimal and uncertainty is high at upper elevations when it comes to recent avalanche activity, snowpack structure, and the amount of dry snow available for transport. If you do make it up there on Thursday, be prepared to make your own assessment. Anticipate larger slabs where there is more dry snow at the surface to drift onto leeward slopes.

    Example of smooth wind slab on the left and scoured snow on the right.

Avalanche Discussion

The likelihood of continued wet avalanche activity should be lower on Thursday due to less precipitation and gradually cooling temperatures. It’s still wise to avoid spending time below rugged terrain like waterfalls, rock faces, and steep, brushy cliffs holding snow. Wet avalanches and rockfall can still initiate from these features.

With wet, soggy conditions and poor snow quality, folks aren’t exactly lining up to get into the mountains. The few who were out today reported no new avalanche activity and punchy, hollow snow in some areas. 

There is still 1-3’ of snow around Heather Meadows. A profile on Dec 5th at 4400’ 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. The snow surface at mid-elevations is heavily runneled and will make for a variable, uneven crust when it freezes. Lower elevation and many mid-elevation locations have minimal snow and difficult travel. 

West North is ahead of the curve when it comes to the end of rainfall. Some weather stations in West Central and South recorded 1.0” or more of rain while Heather Meadows picked up about a half-inch in the last 24 hours. Most of it fell Wednesday or early Thursday.

 

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