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Avalanche Forecast

Archived

Dec 10th, 2018–Dec 11th, 2018

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Snoqualmie Pass.

Cautious route finding and conservative decision-making are essential. You can trigger avalanches due to significant new snow and wind. Avalanche danger will increase in the afternoon and will be most elevated at upper elevations. Watch for signs of dangerous conditions such as recent avalanches, collapsing, or cracks in the snow.

Discussion

Avalanche Discussion

Variable early season conditions exist. Avalanche Danger will change dramatically as you move through the mountains and as slabs build throughout the day. At lower elevations, well below treeline, shallow snow cover may make travel challenging, but may not pose significant hazard for avalanches. Near and above treeline natural and triggered avalanches are likely and could be big enough to kill you.

The main concern is avalanches due to new snow and wind. Underlying the new snow is a layer of weak facets and surface hoar. As new slabs build, it’s possible to trigger large and surprising avalanches. Watch for shooting cracks in the snow, collapses, or avalanches that break widely over terrain features. These are indicators that you should avoid avalanche terrain.

Snowpack Discussion

Regional Synopsis coming soon. 

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.