Avalanche Forecast

Windy conditions the last few days transported the recent snow and formed slabs on the lee sides of ridges and along exposed mid-slope features. Even, though these wind slabs are more than 24hrs old, you’ll want to give them a wide berth Thursday. Take time to identify and avoid any steep slope with smooth pillow-like drifts, below cornices, or where you find firm hollow snow. Expect wind slabs to grow larger and harder to manage as you travel higher in the terrain or move into more wind prone areas. 

On Wednesday avalanche professionals in several locations around the West-North region reported both natural and human triggered wind slabs 8-12” deep. While wind affected snow was found on all aspects, many of these avalanches occurred on NE-E facing slopes. Storm totals from the area ranged from 8-14” for most locations.

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.

On Thursday partly cloudy skies and cold air temperatures will do their best to keep the strong March sun at bay and the snow dry. However, if the sun comes out for more prolonged periods of time, you could see it affect the surface snow, potentially causing it to become unstable. You’ll notice this first when the new snow sheds from rocks and trees. As the snow becomes wet and sticky, you could see new rollerballs and loose wet avalanches. If you see fan-shaped debris, steer clear of similar slopes. In larger steeper terrain, these loose slides could entrain most of the new snow and grow large. 

If you encounter natural loose wet avalanches, that means the sun is winning the battle. This could also indicate it may be weakening large cornices. Don’t linger below these ticking timebombs.

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.