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Avalanche Forecast

Archived

Dec 11th, 2019–Dec 12th, 2019

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

Regions

Stevens Pass.

A potent winter storm will bring heavy snowfall and strong winds Wednesday night and Thursday. Slab avalanches may become easily triggered and widespread on high elevation slopes. Give the storm snow time to stabilize, and seek out low-angle, supported terrain away from overhead hazard.

Discussion

So far this season, avalanche activity has been minor and infrequent due to low snow. Over the next 24 hours, this storm will bring rapid change and create dangerous avalanche conditions at upper elevations. Snow levels will fluctuate between 3500-4000ft, and over 1ft of new snow may accumulate above 4500ft by late afternoon Thursday. Snow totals, along with the avalanche danger will noticeably increase as you gain elevation.

Don’t let the excitement of this first major winter storm distract you from making informed and conservative decisions. Be cautious if you decide to venture into the backcountry on Thursday. Ease into terrain slowly and gather information along the way. Getting caught in even a small avalanche would be a rough ride with high consequences in these early season conditions. Expect to encounter shallowly buried objects and challenging travel conditions.

The incoming snow will fall on a thin snowpack at upper elevations and mostly bare ground below 5500ft. North-northwest facing slopes of the Chiwaukum Range. 12/11/19. Photo: Josh Hirshberg

Snowpack Discussion

Regional Synopsis Coming Thursday, December 12, 2019

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.