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Avalanche Forecast

Archived

Dec 30th, 2019–Dec 31st, 2019

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

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Expect dangerous avalanche conditions to develop during the day and continue Tuesday night as a powerful storm impacts the region. Loose wet avalanches will become increasingly likely at lower and mid elevations as snow changes to rain. Slab avalanches are more likely at upper elevations and will be larger on lee slopes with wind drifted snow.  

Discussion

A warm and windy storm system will impact the area on Tuesday with potentially a wide range of weather outcomes driving how quickly avalanche conditions change across the zone. If the Crystal area is blocked and sees significantly lower precipitation totals than Paradise, expect a lower avalanche danger in this area. In addition, the potential for a period of freezing rain in the White Pass area on Tuesday would also lower the avalanche danger in part of the zone. However, this storm shakes out, expect wet snow avalanche problems to climb in elevation as the day wears on. 

Fresh observations from the White Pass area suggest that recently buried weak snow only a few inches from the surface may have been destroyed over the last few days. New storm slabs that develop on Tuesday may fail within new storm layers or break down to this interface in areas it has been preserved. Much deeper in the snowpack, we are continuing to track a persistent weak layer about a foot above the ground on W-N-E aspects above 5800’ in the Crystal and White Pass areas. This interface has been dormant since the last major storm cycle, but we will continue to think about the potential for very large avalanches as we get deeper into this storm cycle. 

Due to low snow depths, difficult travel conditions and early season hazards are still a factor at all elevation bands. 

Snowpack Discussion

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

Problems

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.