Avalanche Forecast
Regions: Mt Hood.
The avalanche danger will increase sharply by late Sunday afternoon and evening with human triggered slides becoming likely. Choose a conservative travel plan and make sure your plan allows for a safe exit if conditions deteriorate quicker than expected.
Detailed Forecast
Light snowfall Saturday night and Sunday morning will increase in intensity Sunday afternoon along with increasing winds. A warming trend should lead to inverted storm snow by later Sunday afternoon. Snow should change to rain at lower elevations.Â
Natural loose wet avalanches will become very likely on steeper slopes below treeline with the change to rain Sunday afternoon.Â
Shallow storm slab avalanches may bond poorly within storm layers or to the underlying crust. New wind slab should form on N through SE aspects near and above treeline.
All of this will lead to increasing avalanche danger Sunday. Expect human triggered avalanches to be likely as the afternoon wears on. Be prepared to curtail your trip early if conditions become sensitive earlier than forecast.Â
More significant warming and precipitation is expected Sunday night and a natural avalanche cycle is expected.Â
Snowpack Discussion
A storm system hit the Northwest last weekend with strong west to northwest winds. NWAC sites at Mt Hood picked up about 2-3 ft of snow with a good cooling trend. However, strong northeast winds hit at the tail end of the storm Monday and Tuesday. This transported recent storm snow and formed some local wind slab on non-traditional lee aspects near and above treeline.Â
An upper ridge over the coastal waters tilted inland Wednesday and Thursday producing sunny weather and warm temperatures at higher elevations. This may have caused some snowballing and wet loose avalanches on steep slopes facing the sun at Mt Hood. Mt. Hood Meadows pro patrol reported light snow remaining on sheltered slopes below treeline. They also confirmed the unusual wind direction earlier in the week had scoured traditional lee aspects.  One of our biggest concerns heading into the upcoming weekend storm will be the new storm snow's ability to bond to a variety of snow surfaces; near surface facets, wind board, melt-freeze crusts, etc. Â
A generally strong mid and lower snowpack is expected at Mt Hood.
Avalanche Problems
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: Very Likely
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: North, North East, East, South East.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1