Avalanche Forecast

While there is some uncertainty to just how much rain and snow will fall in the Mt. Hood area over the next 24 hours, we know that the upside down layering of the new snow that does accumulate will build denser slabs on top of drier, colder snow received over the last few days. We also know that strong and sustained westerly winds will continue to build deeper slabs on lee slopes near and above treeline throughout the storm.

Expect that you will trigger an avalanche on any slope steeper than 35 degrees. It's on larger open slopes near and above treeline with deeper drifted snow that avalanches may be large enough to injure, bury, or kill a person.

Watch for cracking in the snow as a sign that you can trigger an avalanche in the new snow. Natural avalanches are the most direct sign that the new snow is unstable and to avoid all avalanche terrain.

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.

With rising snow levels on Monday and a change to rain at lower elevations, skier triggered or natural loose wet avalanches are likely on steep slopes. Look for signs that you may trigger a loose wet avalanche such as wet unconsolidated surface snow deeper than your ankle and natural clues like roller balls, trees dripping, or natural wet avalanches. 

Loose wet avalanches may become large in isolated areas where they run longer distances and entrain more recent snow. Remember that even small loose wet avalanches can be more powerful than you expect and can push you into trees, rocks or other obstacles.

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.