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Archived

Avalanche Forecast

Dec 10th, 2018–Dec 11th, 2018
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Stevens 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. 

Avalanche Problems

Storm Slabs

You can trigger avalanches where about 1 foot fresh snow accumulates. These avalanches will generally be soft and confined to steep slopes. At upper elevations and in wind-exposed terrain, you may find stiffer slabs that could break more widely. On low elevation, below treeline slopes you may encounter small wet avalanches. Use extra caution on slopes over 35 degrees and avoid deeper drifts of snow near and above treeline.

Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. 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.

 

You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.

 

Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 1