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Avalanche Forecast

Archived

Feb 16th, 2017–Feb 17th, 2017

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

Regions

Olympics.

Cooling should reduce the potential for wet slab and wet loose avalanches through the day on Friday. Use caution on steeper and unsupported terrain, especially in areas lacking a strong near-surface crust. 

Detailed Forecast

Continued cooling with light snow showers are expected overnight Thursday and early Friday. Friday should remain mostly cloudy with a chance of a few light showers.

This weather will help to decrease the avalanche danger by allowing a surface crust to form and remaining liquid water to drain. However, the recent heavy rains may have left liquid water in the upper snowpack, making wet snow avalanches still possible Friday.  

Wet slab avalanches are hard to predict and potentially powerful due to the high water content within the slab. The wet slab potential is decreasing through Friday, but extra caution is advised, especially on steeper and unsupported terrain, especially in areas lacking a strong near-surface crust.

The forming near surface crust should help the stabilization process by Friday, but warming afternoon temperatures may weaken or melt surface snow. Watch for areas where the crust is breaking down or where wet snow is becoming more than a few inches deep. 

Snowpack Discussion

Weather and Snowpack

A rain event beginning last Wednesday 2/8, left a strong rain crust with varying amounts, up to about 8 inches of new snow accumulating at Hurricane, by Saturday 2/11. Strong west winds, exposed a firm and slick crust on windward aspects in many areas.  

High pressure last 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 about 8 inches of snowpack settlement at Hurricane Ridge.  

Another atmospheric river impacted the PNW beginning Tuesday night. Heavy precipitation at high snow levels fell throughout the Olympics and west slopes of the Cascades. Hurricane Ridge received over 2.5 inches of rain by Thursday morning.

A slow cooling trend began overnight with only light showers with little to no new snow accumulations at Hurricane Ridge by Thursday evening.

The wet snowpack is beginning to drain and slowly refreeze as of Thursday evening. 

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.