Avalanche Forecast
Regions: Mt Hood.
On Mt Hood the main problem Friday, is expected to be wind slab in near and above treeline zones. Wet snow conditions may be slow to refreeze and strengthen at lower elevations.
Detailed Forecast
Another front should arrive Friday, bringing additional moderate snowfall at lower snow levels. Winds should be strong, especially near and above treeline. The main concern Friday will be newly forming wind slab on lee exposed slopes, especially NW-N-SE facing near and above treeline.Â
With cooling temperatures, the new snow should have a favorable profile.
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Snowpack Discussion
A warm front last Thursday caused heavy rain on the volcanoes but with lighter rain at Mt Hood. This caused an avalanche cycle and consolidation along the Cascade west slopes and Mt Hood.
This was followed by cooler weather and some snow. NWAC stations at Mt Hood indicate about 6-9 inches for the 2 days ending Sunday morning.
The Mt Hood Meadows pro patrol Sunday near tree line reported isolated 2-6 inch storm slabs released by ski cuts on lee N-NE slopes. A stable surface crust was reported below tree line.
The Mt Hood Meadows pro patrol Monday reported some roller balls on solar slopes but no avalanches. There was about 6-8 inches of loose snow on non solar slopes in the near and above treeline.
Very mild, above freezing weather Wednesday allowed for wet surface snow conditions in most areas.
Mild weather continued Thursday with heavy rain reaching at least 8000 feet on Mt Hood, causing increasing wet snow conditions.Â
Snow levels dropped late Thursday as temperatures lowered some 10 degrees or more through the day. This has changed rain to snow gradually, likely allowing a favorable bond to form between new snow and the old wet snow surface.
Avalanche Problems
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: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1
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: Unlikely
Expected Size: 1 - 1