Avalanche Forecast

This has been a prolonged gradual warm-up and loose wet cycle. We really haven’t seen a widespread avalanche cycle yet, which would “flush” out lingering instability. Instead, in nearby zones, each day, several more natural small (and a few large) loose wet avalanches appear, mostly on S-W aspects. Expect this pattern to continue on Thursday. In the morning cool temperatures and a frozen snow surface will limit the loose wet hazard. Sunshine will help temperatures warm quickly and you’ll start to notice the snow surface softening. There’s a big difference between “soft” and “weak”. When you find more than 4” (ankle deep) wet snow on the surface, you’re moving into the weak and unstable zone. This could be your clue to seek out slightly firmer slopes on other aspects. 

The snowpack has not transitioned to a spring-time state and several cold layers and crusts still exist. As the warm weather drags on, you could see water percolating to these layers allowing for larger slab or glide avalanches. Be leery of large complex sunny terrain during the hottest parts of the day.

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.

Cornices have grown large and looming after a winter of big snowfalls and strong winds. Now as the weather turns warm, you could see more of these giants falling down. Choose routes that minimize the amount of time you spend below these time-bombs. Even if you are in the shade, the cornice may be in the sun. Falling cornices, or any avalanche, may act as a very large trigger producing deeper slab avalanches. This occurred on the SW side of Goat Mt. in the West North zone on Sunday when a loose wet slide released a very large slab. 

On steeper northerly slopes, you may still find cold dry snow hiding in the shadows. In these areas, remember you just changed snowpacks. Turn your attention to signs of wind affected snow. Take time to carefully assess steep lines for signs of wind loading prior to committing to a slope.

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind lips of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

Cornices can never be trusted and avoiding them is necessary for safe backcountry travel. Stay well back from ridgeline areas with cornices. They often overhang the ridge edge can be triggered remotely. Avoid areas underneath cornices. Even small Cornice Fall can trigger a larger avalanche and large Cornice Fall can easily crush a human. Periods of significant temperature warm-up are times to be particularly aware.

A corniced ridgeline. A large cornice has formed at the top of the ridge. A smaller cornice has formed to the left of the trees from crossloading.

Cornices are easy to identify and are confined to lee and cross-loaded ridges, sub-ridges, and sharp convexities. They are easiest to trigger during periods of rapid growth (new snow and wind), rapid warming, and during rain-on-snow events. Cornices often catch people by surprise when they break farther back onto flatter areas than expected.