Rain and continued mild temperatures on Sunday will maintain wet snow and avalanche conditions at all elevations in the Mt. Hood area. Avoid steep open slopes above terrain traps where being caught in even a small loose wet avalanche could have serious consequences. To mitigate the low likelihood/high consequence wet slab avalanche problem, avoid steep open slopes above treeline. At lower elevations, limit your exposure to avalanche paths that originate at higher elevations.
Summary
Detailed Forecast
Rain and continued mild temperatures on Sunday will maintain wet snow and avalanche conditions at all elevations in the Mt. Hood area.
Loose wet avalanches are most likely during and following periods of higher rainfall. Avoid steep open slopes above terrain that could magnify the consequences of an avalanche. Cliffs, open creeks, rocks, and gullies are all examples of terrain traps where small avalanches may injure or kill you.
The likelihood for large and destructive wet slab avalanches originating from above treeline should decrease on Sunday. However wet slab avalanches are extremely difficult to predict and if they do release, they will entrain significant amounts of snow and travel well into lower elevations. To mitigate this low likelihood/high consequence problem, avoid steep open slopes above treeline. At lower elevations, limit your exposure to avalanche paths that originate at higher elevations.
Snowpack Discussion
W-NW winds were strong at Mt. Hood on Saturday but due to continued mild conditions, there is no snow available for transport in the above treeline band (NWAC's forecast does apply above 7000-8000 feet). The recent mild and at times wet weather has created wet surface snow conditions well into the above treeline terrain in the Mt Hood area.
The upper snowpack consist of a mix of wet snow, old crusts, and well consolidated storm snow.
Observations
Mt. Hood Meadows pro-patrol reported that Friday's widespread loose wet 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 weather. Winds were strong near and above treeline but no snow was available for transport in area.
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.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wet Slabs
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 Slab avalanches can be very destructive.
Avoid terrain where and when you suspect Wet Slab avalanche activity. Give yourself a wide safety buffer to handle the uncertainty
A Wet Slab avalanche. In this avalanche, the meltwater pooled above a dusty layer of snow. Note all the smaller wet loose avalanches to either side.
Wet slabs occur when there is liquid water in the snowpack, and can release during the first few days of a warming period. Travel early in the day and avoiding avalanche paths when you see pinwheels, roller balls, loose wet avalanches, and during rain-on-snow events.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Feb 4th, 2018 12:11PM
