Avalanche Forecast

We’re several days into this loose wet pattern now and many natural avalanches already occurred. Clear skies and cool temperatures should help the snow surface freeze in most locations. Expect that to change quickly Wednesday morning as a strong March sun helps temperatures soar, softens the snow, and increasing the avalanche danger.  Pay attention to the snow surface. When you start to notice you boot sinking in near your ankle, it’s time to change aspects. Unstable snow will move around the compass as the sun moves across the sky. Don’t forget about how this could affect slopes you’ll need to cross to return to your car later in the day. 

On Wednesday, we’ll be entering our 3rd full day of above freezing temperatures. As we do so, water may begin to impact layers deeper in the snowpack. This could allow for isolated larger slab or glide avalanches. Limit your exposure to large complex terrain during the warmest 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. 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.