Avalanche Forecast
Regions: Mt Hood.
This is a time of the year when you often need to watch for both winter and spring types of avalanche conditions. It is always good to read the forecast for details.
Detailed Forecast
Light winds and sunny weather with warmer temperatures should be seen on Wednesday.
The sun will be out and stronger and the days are getting longer. It is hard to say how much of a problem loose wet avalanches might be on Wednesday. Watch for wet snow deeper than a few inches or rollerballs or pinwheels on steep solar slopes. The problem of loose wet avalanches should not be extensive but limit your terrain choices if you see more activity than expected.
Wind transported snow from last Friday and Saturday is most likely to linger on unusual south to northwest facing slopes on Wednesday. But on most slopes the sunny weather will have caused these layers to bond with underlying layers and it should no longer be a problem.
Cornices will not be listed as a problem yet but start to practice checking the ridges for these as we shift into spring.
Due to the low snowpack, especially below treeline, watch for terrain hazards such as open creeks, partially covered rocks and vegetation. Many areas below treeline do not have enough snow (new or existing) to pose an avalanche hazard.
Snowpack Discussion
The latest snowfall in the Cascades was Wednesday to Friday when about 4-10 inches fell near and above treeline at Mt Hood.
This was followed by strong northeast winds in the Cascades and at Mt Hood Friday and Saturday.
The Mt Hood Meadows patrol reported sensitive new wind slab Friday morning at about 6600 feet on northeast slopes with soft wind slabs around 1 foot easily releasing.Â
By Saturday the recent surface snow had been stripped from most slopes above 6500 feet. The winds were so strong to have blasted the shallow surface snow to who knows where, rather than steadily building new wind slab layers. Nonetheless pockets of wind slab will need to be watched for on a variety of terrain features.
Minor cooler weather on Sunday and Monday has been followed by sunny weather on Tuesday. East winds remained pretty weak Monday night. This weather will have caused consolidation and stabilizing.
The mid and lower snowpack at Mt Hood consists of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.
Avalanche 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: South East, South, South West.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 1
Wind Slabs
Release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..
Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.
Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.
Aspects: South, South West, West, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1