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Avalanche Forecast

Archived

Mar 31st, 2017–Apr 1st, 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, human triggered possible.

Regions

Mt Hood.

Loose-wet snow avalanches should remain possible in steep terrain. Use caution in steep terrain, especially if the surface snow is wet more than a few inches, avoiding steep slopes above terrain hazards such as trees or cliffs. Avoid travel on or below cornices. 

Detailed Forecast

A warm, sunny day Friday allowed for further shallow melt and consolidation. Increasing clouds Friday night with light precipitation should maintain mild temperatures and allow for limited surface crust formation.

This weather should maintain shallow, moist to wet surface snow conditions Saturday.

Only light amounts of additional precipitation with a gradual cooling trend are expected Saturday. This should not appreciably change the overall avalanche danger through the day Saturday.

Expect shallow wet snow conditions over one or more strong near surface crust layers.

Recent shallow wind slabs should have mostly stabilized where formed on lee slopes, mainly above treeline and on NW-SE aspects.

Recent cornices are very large. Natural cornice releases and resulting slab avalanches are dangerous and unpredictable. Give cornices a wide berth if traveling along ridge-lines and avoid slopes directly below large cornices. See a blog post regarding cornices here. 

Snowpack Discussion

Weather and Snowpack

Let's just say it's been a wet and wild few weeks regarding weather and avalanches in the Cascades. 

This past week has also been active weather-wise, with another strong front on Sunday, but water amounts/snowfall totals have been slightly lower relative to the extreme wetness of the past few weeks. In the last 5 days ending Monday morning NWAC stations at Mt Hood have picked up another 2-2.5 ft of snow.

A strong low pressure system brought rising snow levels and locally heavy precipitation Tuesday night through Wednesday along the west slopes of the Cascades including Mt. Hood. After receiving a few inches of snow Tuesday night, Mt. Hood saw periods of moderate to heavy rain above 7000 feet on Wednesday.

Cooling and showery weather Thursday allowed wet snow to begin refreezing with an additional 3-6 inches accumulating in most areas. The strong winds began diminishing Thursday, but continued to transport new and available snow to lee slopes, building fresh wind slabs, mainly above treeline.

Very mild temperatures and strong sunshine Friday, allowed for wet surface snow conditions in most terrain, even northerly facing slopes. Shallow loose-wet snow avalanches occurred Friday on many steep slopes but remained small.  

Recent Observations

On Monday the Meadows patrol found touchy 6-12" but up to 12-18" wind slab on NE slopes near and above treeline. Surface loose wet snow was also becoming evident in the below treeline areas.

The Meadows patrol on Tuesday reported one explosive released 12-20 inch storm slab on an east slope at about 6000 ft. Patrollers also triggered a large cornice on approach. Surface snow was getting wet with some pinwheels in the afternoon.

The storm limited observations on Wednesday, but rain quickly penetrated the upper snowpack in the Mt. Hood Meadows base area by late morning. 

Shallow loose wet avalanches were reported at Mt Hood Meadows and in adjacent backcountry terrain both Thursday and again Friday afternoon.  

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.