Avalanche Forecast
Regions: Mt Hood.
Dangerous avalanche conditions should persist Saturday above treeline, though be improving. Best to be particularly cautious, especially near and above treeline, avoiding steep or wind loaded slopes, watching for sensitive storm layers and wind slab deposits.
Detailed Forecast
A transitory ridge of high pressure should move across the area Saturday to allow for cool weather, light winds and some possible sun breaks. This weather should allow for a slow improving trend as recent storm and wind slab slowly settle and strengthen.Â
Avoid terrain where wind may have built isolated wind slab layers, mainly higher elevations near ridges, most likely on a wide variety of aspects.. Â Â Â
Avalanche problems Saturday should continue to be associated with recent storm and wind slab layers. Avalanches should be confined to the new storm snow since Thursday, but a few may step down to older storm layers or crusts in isolated locations. Â
Terrain anchors are still causing significant anchoring at the lowest elevations. Use caution near creeks which are still open in some areas.
Snowpack Discussion
Another rain event Thursday on Mt Hood caused rain to about 7000 feet. This produced widespread storm snow conditions and released widespread avalanches Thursday. With reports from pro patrol at Mt Hood Meadows indicating sensitive natural and triggered slab releases were occurring as the storm progressed through the day Thursday and temperatures warmed. Many sympathetic and very sensitive slabs were reported, involving the 8-12 inches of storm snow that had been received by mid-morning Thursday. Â
Cooling Thursday night through Friday, and a further 8-12 inches of snowfall is now building new storm layers above a newly forming crust.
Any expected avalanches should now be confined to new wind slab layers, and possibly some storm slab layers, though the cooling trend should limit the extent of storm slab.
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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
Storm Slabs
Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. Storm-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.
You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.
Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 1