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Avalanche Forecast

Archived

Jan 1st, 2020–Jan 2nd, 2020

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

Regions

Snoqualmie Pass.

The avalanche danger you encounter Thursday depends on how much new snow you find. When you come across more than 8 inches of heavy storm snow or find the wind formed snowdrifts, steer around all open slopes greater than 35 degrees. If you discover evidence of strong over weak snow at lower elevations, you can expect the same issue to be larger and harder to manage as you ascend.

Discussion

This is a tricky avalanche forecast because it depends on additional snow associated with a Puget Sound Convergence Zone. This weather phenomenon can lead to high levels of spatial variability with some locations experiencing substantial rain/snow while areas nearby receive very little. The avalanche hazard you encounter will depend on your location in the zone and how the weather plays out Wednesday night. 

Limited information, especially at upper elevations, around Snoqualmie Pass, leave us with a higher degree of uncertainty than normal for this time of year. Take time to make observations and compare them to the forecast. When conditions differ from what you expected, step-back and reevaluate.

Snowpack Discussion

New Regional Synopsis coming soon. We update the Regional Synopsis every Thursday at 6 pm.

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.