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Avalanche Forecast

Archived

Feb 15th, 2017–Feb 16th, 2017

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

Regions

Olympics.

With a fair amount of water in the upper snowpack, wet snow avalanches will maintain dangerous avalanches conditions Thursday. Wet slab avalanches are hard to predict and powerful due to the high water content. Allow the snowpack to stabilize, avoiding steeper slopes and any avalanche terrain where even a small wet avalanche could have serious consequences.   

Detailed Forecast

After a mild and wet Wednesday night, a slow cooling trend is expected on Thursday with light to moderate showers. With a fair amount of water in the upper snowpack, wet snow avalanches will maintain dangerous avalanches conditions Thursday. Wet slab avalanches are hard to predict and powerful due to the high water content, so extra caution is advised. 

Loose wet snow avalanches may begin small but entrain deeper layers. Observations and tests for loose wet avalanches are more straightforward such as wet surface snow deeper than a few inches, rollerballs and natural loose wet avalanche activity.

Allow the snowpack to stabilize, avoiding steeper slopes and any avalanche terrain where even a small wet avalanche could have serious consequences. 

Shallow storm or wind slab may start to form in the near and above treeline elevation bands by Thursday afternoon, but will not be listed among the primary avalanche problems for Thursday. 

Snowpack Discussion

Weather and Snowpack

The 2/8 - 2/10 storm cycle left a strong rain crust with varying amounts of new snow received at the tail end of the cycle. Strong west winds on 2/10 exposed this firm and slick crust on windward aspects in many areas.  

High pressure Saturday to Tuesday brought increasing sunshine and warm temperatures. Temperatures reached the 40's and 50's in many areas of the Olympics and Cascades by Monday and Tuesday. This caused a lot of snowpack settlement, some small loose wet avalanche activity and a decreasing avalanche danger.

Another atmospheric river impacted the PNW on Wednesday. Heavy rain at high snow levels fell along the west slopes of the Cascades and Olympics. 

Recent Observations

No recent observations. 

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.

Wet Slabs

Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.