Avalanche Forecast
Regions: Mt Hood.
The avalanche danger should remain elevated in the morning with a slow decreasing trend through the afternoon as storm instabilities begin to stabilize. Cautious route-finding and terrain selection will be essential on Wednesday to stay safe and avoid storm related avalanche problems.
Detailed Forecast
Moderate to heavy precipitation Tuesday night should moderate on Wednesday. A warming trend should occur Tuesday evening leading to a natural avalanche cycle involving the new storm snow. A slow cooling trend should begin late Tuesday night and continue through Wednesday with transport winds shifting from S-SW to NW by Wednesday afternoon.Â
The avalanche danger should be elevated in the morning with a slow decreasing trend through the afternoon as storm instabilities begin to stabilize. Cautious route-finding and terrain selection will be essential on Wednesday to avoid storm related avalanche problems.Â
Stay off steeper slopes and allow storm instabilities time to settle. Look for wind slab on a variety of aspects near and above treeline due to shifting winds. Watch for signs of firmer wind transported snow that can indicate wind slab layers near and below ridges.
Shallow loose wet avalanches are possible Wednesday below treeline on steeper slopes primarily in the morning.
Snowpack Discussion
About a week of fair weather was centered around the New Year. This allowed the heavy snow that fell during the strong storm cycle that ended about Christmas to settle and stabilize. Moderate to strong east-northeast winds in early January had significantly scoured most of the available surface snow in the near and above treeline elevation bands.
No avalanches have been reported over the past several days on Mt Hood.Â
As of 4 pm Tuesday, a little less than an inch of water received during the day had translated into 5-6 inches of heavy snow at the base Timberline and Mt. Hood Meadows NWAC stations. Warm air has been slow to work it's way around the mountain, with temperatures just beginning to climb above freezing at Timberline Wednesday afternoon while still below freezing at Meadows. Winds have been strongest above treeline from the south or southwest. 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.
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: 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.
Elevations: Below Treeline.
Likelihood: Likely
Expected Size: 1 - 1