Avalanche Forecast

Strong to extreme winds on Wednesday likely caused erratic loading patterns and may have formed wind slabs further downslope than usual. Be suspicious of any steep slope with freshly drifted snow, especially above treeline where temperatures have remained cooler and wind slabs may be easier to trigger. 

Check the bond of the new snow to the crust underneath before committing to slopes steeper than 35 degrees. If you suspect wind slabs are present, you can travel safely by sticking to ridgelines, scoured windward slopes or by choosing lower angled terrain. 

Even for a place that gets as much snow as Mt. Hood, January has felt like one long continuous storm cycle. You still need to think about what’s happening high on the mountain and limit your exposure if crossing canyons and gullies at lower elevations connected to terrain capable of producing very large avalanches.

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.

The most likely place to trigger a loose wet avalanche should be lower and mid-elevations and on very steep (40+ deg) terrain features. More snow is available for entrainment in the 5000-6000’ range and it’s at these elevations that loose wet avalanches could become large and dangerous. Above treeline, winds and afternoon cloud cover will likely limit the loose wet potential. 

While loose wet avalanches may be stubborn to trigger, you don’t want to get caught in one at any elevations where heavy wet snow could push you off a cliff, into an open creek or combine with other terrain traps. If the sun makes an appearance Thursday morning, pay attention to steep sunny slopes for increasing signs of instability. If you see roller balls, pinwheeling or natural loose wet avalanches, it’s time to avoid nearby 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.