Avalanche Forecast
Regions: Mt Hood.
On Mt Hood Saturday, the main problem has now shifted to new snow instabilities, above the new rain crust. New areas of wind slab on lee wind exposed terrain, near and above treeline. Wind slabs may have formed on a variety of aspects due to highly variable wind directions. Watch for new cornices near ridges.
Detailed Forecast
Cool weather with light snow showers and moderate westerly winds Saturday should allow for an overall slowly decreasing danger. Weak lower density snow that may exist above the new crust will slowly settle, but remain reactive to human triggers Saturday.Â
The greatest avalanche problem should be sensitive wind slabs on lee slopes, mainly NW-N-SE facing slopes, especially below ridges, near and above treeline.Â
Watch for newly formed cornices along ridges as well. These may be sensitive to human triggers.
Below treeline, watch for any wind affected snow on exposed terrain features such as cross loaded ribs and larger open slopes.
Snowpack Discussion
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, caused increasing wet snow conditions.Â
Snow levels dropped late Thursday as temperatures lowered some 10 degrees or more through the day. The bond of new snow to crust is reportedly strong in the Mt Hood zone Friday, however weak snow above the crust is making for some sensitive ski triggered wind slabs near treeline on N-E facing the wind loaded terrain. No observations were received above treeline due to storm conditions.Â
Below treeline, shallow new snow was not reactive overlying the new crust.Â
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.
Elevations: Treeline, Below Treeline.
Likelihood: Possible
Expected Size: 1 - 1