Avalanche Forecast

Issued: Feb 6th, 2018 12:10PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Loose Wet.

Northwest Avalanche Center NWAC, Northwest Avalanche Center

It will be possible to trigger a loose wet avalanche during solar heating on Wednesday. Avoid steeper solar slopes if wet surface snow becomes deeper during the afternoon hours and don't expose yourself to cliffs or terrain traps such as gulleys.

Summary

Detailed Forecast

Continued very warm and warming temperatures along with partly cloudy skies will increase the possibility of loose wet avalanches on Wednesday.

The thick 10-12" crusts formed on Monday (1/5) will take time to melt, but as freezing levels continue to rise and the sun adds energy to further melt the snow, expect boot penetration to increase and enough wet snow will thaw to make triggering a loose wet avalanche possible. At all elevations, avoid steeper solar slopes where wet, slushy snow becomes deeper than a few inches.

Snowpack Discussion

Warming aloft created inversion conditions on Tuesday, but all elevations warmed above freezing by afternoon, allowing previously firm crusts an initial opportunity to thaw. Low clouds were seen near the top of the inversion.

Cooling from Sunday afternoon through Monday refroze the top 10-12" of wet surface snow into a firm crust.

Moderate to strong W-NW winds were seen over the weekend at Mt. Hood, but due to continued mild conditions, there is no snow available for transport in the above treeline band (NWAC's forecast does not apply above 7000-8000 feet). The mild and at times wet weather created wet snow conditions well into the above treeline terrain in the Mt Hood area. 

The upper snowpack consist of a mix a thick crust at the surface, wet snow, old crusts, and well consolidated storm snow. 

Observations

Mt. Hood Meadows pro patrol reported that wind kept the snow firm except at the lowest elevations receiving solar heating. Runnels were in the terrain up to 7300'.

Mt. Hood Meadows pro patrol reported that Friday's widespread wet loose avalanche activity had become more stubborn and isolated near and below treeline by Saturday.  The wet upper snowpack was still quite unconsolidated with the most recent 1/18 crust breaking down due to the sustained mild wet weather. Winds were strong near and above treeline but no snow was available for transport in area. 

Problems

Loose Wet

An icon showing Loose Wet

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. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. 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.

 

Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.

 

Several loose wet avalanches, and lots of pinwheels and roller balls.

Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.

Aspects: East, South East, South, South West, West.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 1

Valid until: Feb 7th, 2018 12:10PM