Avalanche Forecast

This storm is bringing large amounts of water along with warming temperatures, making for dangerous avalanche conditions. Observations show that new snow from Wednesday night was low density and did not bond well to the old snow surface. As the slab thickens on top of the 12/18 interface, mid-storm bonding may also be problematic due to heavier snow over the low density snow. Strong winds will cause slabs to become thicker and more reactive in wind-loaded terrain. Natural slab avalanches are expected, potentially stepping down into deeper layers of snow in isolated areas. As freezing levels rise and a switch to rain takes place below ~5500 feet, natural avalanche activity will be more widespread. The danger is peaking Thursday night and continuing into Friday morning. Friday is a good day to avoid traveling in and below 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.

Loose Wet avalanche activity is likely to take place at the onset of rain and can trigger slab avalanches by breaking into deeper snow layers where present. These avalanches are capable of entraining lots of snow and running far distances, even on low angled slopes. With the current low snow totals below treeline, there is a fair amount of uncertainty when it comes to the potential size of these avalanches. Regardless, the warmup and rain will create heavy snow and challenging travel conditions in addition to the increased danger. Avoid traveling in and below all avalanche terrain.

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.