Avalanche Forecast

The loose wet avalanche cycle didn’t get a chance to run its course in many areas Wednesday. That means there’s still plenty of cold snow to be affected by the sun. We aren’t sure if the loose wet avalanche cycle will turn-on Thursday, but you should be on the lookout for it. Small changes in cloud cover or thickness could lead to large changes in avalanche conditions. If you see new roller balls, fan-shaped avalanche debris, or experience moist surface snow, loose wet avalanches can occur. When you see these signs, steer away from similar slopes.

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.

Thursday isn’t a day to get caught up in semantics. Locations across the West-South seem to be dealing with different types of slab avalanches. Here are the common themes. Slabs in every area are a few days old and becoming harder to trigger. As a general rule, slab avalanches can be difficult to assess and predict. Be leery of any feature where you are more likely to trigger an avalanche such as near convex rollovers, on unsupported slopes, in locations where the wind drifted the snow, and in areas where the new snow is shallow. Where ever you travel, don’t try to outsmart these lingering slab avalanche problems.

Details: Storm slabs may be largest in areas such as Paradise where the most snow accumulated during this storm. In some locations, particularly around Crystal, you may find a weak layer of snow 18-20 inches below the snow surface. This layer has been lingering in the snowpack for quite some time and is still producing results in snowpack tests. Wind prone areas, such as White Pass, may see only wind drifted slabs. Use observations as you travel to identify which of these scenarios you are most likely experiencing.

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.