Avalanche Forecast
Regions: Mt Hood.
Expect deeper, more sensitive, and dangerous wind slabs to continue building above treeline Monday. Wind slabs at lower elevations will be harder to trigger but still possible on the right steep open slope or in a recently cross-loaded gully. If the sun comes out, expect small, natural loose avalanches to occur on steep and rocky slopes.
Discussion
Avalanche and Snowpack Discussion
Following rain and freezing rain Saturday, 10-12 inches of snow accumulated Saturday night and Sunday with strong west to northwest winds slowly easing during the day on Sunday. Mt. Hood Pro-patrol found fresh but stubborn wind slabs up to 2' deep near treeline. More importantly, wind slabs had developed on unusual aspects, cross-loaded slopes and formed on open slopes below treeline. Winds had scoured ridges to the most recent firm icy crust in many areas. We have no recent observations from above treeline due to the recent stormy conditions.Â
Snowpack Discussion
Updated Regional Synopsis coming soon
Avalanche Problems
Wind Slabs
Strong winds formed new wind slabs in all elevation bands Sunday. Mt. Hood Meadow Pro-partol reported wind loading in unusual locations, including cross-loaded gully features. Wind slabs like this can be tricky to manage as they often don’t seem very reactive, luring you out onto the slab. If you see fresh cornices, wind drifted snow, or feel firm, hollow, surface snow, wind slabs are nearby. Expect more dangerous conditions above treeline as moderate north winds continue to move new snow and build deeper wind slabs. Near and below treeline, recently formed wind slabs should be more stubborn and harder to trigger.
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.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 1
Loose Wet
When the sun comes out Monday, you will see loose snow avalanches on steep, rocky, and sunny slopes. Don’t get surprised by this easy to anticipate avalanche problem. If you see rollerballs or observe new fan shaped avalanches, avoid confining gullies and high consequence slopes where even these small avalanches can hurt you.
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.
Aspects: South East, South, South West.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 1