Avalanche Forecast
Regions: Mt Hood.
A strong storm will create dangerous avalanche conditions Wednesday. Strong winds and heavy snow will quickly build wind slabs on lee slopes. Mixed rain and snow at lower elevations will make wet avalanches likely.
Discussion
There is uncertainty in the weather models about the timing of the snow levels lowering Tuesday night and Wednesday morning. How soon the rain switches to snow Tuesday night will play a big factor in the distribution of wind slabs and wet avalanches. Pay attention to changing conditions and be prepared to make your own observations and assessments as you travel.
Snowpack Discussion
New Regional Synopsis coming soon. We update the Regional Synopsis every Thursday at 6 pm.
Avalanche Problems
Wind Slabs
Strong winds will build fresh wind slabs on lee slopes, especially at upper elevations. Avoid steep slopes with wind drifted snow. Wind slabs will continue to grow Wednesday and as the slow level drops during the day, expect to find wind slabs developing near treeline.
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: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1
Loose Wet
Mixed rain and snow at mid and low elevations Tuesday night will prime conditions for loose wet avalanches. If you see rollerballs or natural loose wet avalanches, avoid nearby steep slopes where you find wet unconsolidated surface snow. Wet loose avalanches are often more powerful than you'd expect. Avoid extreme terrain where even a small avalanche could rake you through rocks, stumps or push you into open creeks.
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.
Elevations: Treeline, Below Treeline.
Likelihood: Likely
Expected Size: 1 - 1