Avalanche Forecast

The recent storm snow landed on a variety of surfaces from surface facets and surface hoar on shaded aspects to melt freeze crusts on southerly aspects. The slightly warmer temperatures associated with the storm, along with fairly strong windds likely built slabs in upper elevation and exposed areas. The recent heavy wind loading transported snow-both new and old, onto leeward slopes. The snow may fracture quite wide on shaded aspects where the recently buried layer is weak and faceted. Any avalanches on the old surface may step down a foot or so to layers from early March. Slides may run quite a distance, encompassing much of a terrain feature at upper elevations. Check for thick, cohesive layer of snow sitting over a weaker snow layer. If you see obvious signs of instability such as shooting cracks and recent slab avalanches on small steep slopes, it is time to stay off of, and out from underneath steep open slopes.

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.

With new snow sitting over a crust, and the strong sun of mid March about to make an appearance, expect loose wet avalanches to become common by late morning. These will begin first on east and southeasterly aspects, and continue onto south and southwest aspects as the afternoon rolls on. Look for signs of loose wet instability such as heavy wet surface snow, rollerballs, and fan shaped avalanches. The larger the slope, the large these slides may become. If you notice these clues, heed the warning signs and avoid going underneath steep slopes where loose wet slides may run naturally. 

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.