Avalanche Forecast
Issued: Mar 20th, 2018 11:55AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Wet.
NWAC,
Northwest Avalanche Center
You might trigger a small Loose Wet avalanche as rainfall moistens cold snow on polar aspects, Wednesday. If you encounter active rainfall, roller-balling, or natural Loose Wet avalanches, avoid travel on those steep slopes.
Summary
Detailed Forecast
Avalanche danger will increase very slightly during the day on Wednesday at lower elevations where increasing light rain moistens cold snow on polar aspects.
Loose Wet avalanches are possible where cold snow soaks up enough rain water to become unstable. If you encounter active rainfall, roller-balling, or natural Loose Wet avalanches, avoid travel on those steep slopes.
Snowpack Discussion
After several days of spring-like weather with light winds and a strong diurnal temperature signal, soft snow still remains on polar aspects while melt-freeze conditions have been reported on non-polar aspects and very minor loose wet avalanche activity was observed in response to Tuesday's warm weather and sunshine, indicating that loose wet activity has generally run its course on non-polar aspects.
Friday night and Saturday brought 9 inches of snow in the Timberline area, with only a few inches of new snow in the Mt Hood Meadows area. The new snow fell with cool temperatures and some moderate westerly winds near ridge crest Friday night. The most recent snow sits atop another melt-freeze crust.
Several melt-freeze cycles the weekend of March 10-11 helped to consolidate the snowpack.
While we are tracking several layers deeper in the snowpack, there are currently no significant layers of concern.
Observations
On Tuesday, MHM pro patrol reported shaded terrain holding soft snow while the sun was softening snow surfaces on non-polar aspects. Very minor loose wet activity was reported below treeline. He noted that the NWAC Cascade Express station at MHM was reading higher than observed temperatures on Tuesday due to its proximity to a dark roof surface.
On Sunday, MHM pro patrol reported no reactivity to any older shallow wind slabs with only very shallow surface snow becoming moist.
On Friday, Pro-observer Laura Green found 2-4" of new snow near Timberline well bonded to the underlying crust. Poor visibility limited observations above treeline.
Problems
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.
Elevations: Below Treeline.
Likelihood
Expected Size
Valid until: Mar 21st, 2018 11:55AM
