Avalanche Forecast
Issued: Apr 5th, 2018 12:29PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Wet.
NWAC,
Northwest Avalanche Center
Wet snow conditions will persist Friday with large Wet Snow avalanches possible In isolated areas. Loose Wet avalanches are now possible at all elevations. Avoid slopes with terrain traps where you see evidence of new rollerballs, pinwheels, and small Loose Wet avalanches. Recent rain and warm temperatures have weakened Cornices so give them a wide berth and be aware of overhead hazard.
Summary
Detailed Forecast
After a likely soaker of a storm Thursday afternoon and night with a rising snowline, relatively drier and warm conditions are expected Friday. Wet snow conditions will persist, with large and destructive wet snow avalanches possible in isolated areas Friday.
Loose Wet avalanches are now possible at all elevations. In isolated areas, Loose Wet avalanches may become large if they gouge down to deeper layers. Avoid slopes with terrain traps where you see evidence of new rollerballs, pinwheels, and small Loose Wet avalanches.
If water reaches buried crusts or softer layers of snow, Wet Slab avalanches could occur. Wet Slabs are hard to predict and can be very destructive. If you see slab avalanche activity during periods of rain, avoid traveling in avalanche terrain.
Glide avalanches are possible in isolated areas below treeline with a smooth rock bed surface. In these specific terrain features, the entire snowpack may release if lubricated with water due to recent rainfall and sustained periods of above freezing temperatures. Look for glide cracks as a precursor that large and dangerous natural glide avalanches are possible. Glide avalanche releases are not tied to peak warming or rainfall and are difficult to predict.
Recent rain and warm temperature have weakened Cornices. Give Cornices a wide berth if traveling along ridgelines as they often break back further than expected. Be aware of overhead hazard if traveling on slopes with Cornices above as they may fail naturally or be human-triggered.
Fresh or recent Wind Slabs may exist at the top or just outside our above treeline elevation band (~7500 ft) on lee slopes. Use visual clues such as blowing snow, fresh cornices, and cracks in the snow all indicate you could trigger a Wind Slab avalanche.
Snowpack Discussion
Rain and a rising snowline allowed wet snow conditions to extend to near and above treeline by late Thursday afternoon.
12-14 in. (30-35 cm) of snow fell in the Mt Hood area Sunday and Monday. Strong westerly winds during the storm and through the day Tuesday redistributed much of the recent snow at higher elevations, forming wind slabs on lee slopes.
There are currently no significant layers of concern in the mid or lower snowpack.
Observations
No avalanches were reported Wednesday or Thursday.
Tuesday, Mt Hood Meadows pro patrol reported Wind Slabs releasing with explosives on N-E lee slopes above treeline, averaging 1 ft. Wind Slabs were no longer sensitive to ski triggering. Below treeline, storm layers had settled and stabilized with no avalanches reported near or below 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.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Apr 6th, 2018 12:29PM
