Avalanche Forecast
Regions: Mt Hood.
While recent storm related avalanche problems will have greatly diminished by Saturday, isolated areas of wind slab may remain on lee N through SE slopes near and above treeline. Also, loose wet avalanches will be possible on steeper solar slopes, especially if there are prolonged periods of sunshine.
Detailed Forecast
Variable cloud cover on Saturday will be accompanied by generally light winds and rising freezing levels. An incoming frontal system arriving Saturday night should spread high clouds over the area in the afternoon. Mt. Hood may see more cloud cover than areas further north on Saturday which would limit the loose wet avalanche potential in this zone.Â
Recent storm related avalanche problems will have greatly diminished by Saturday. Isolated areas of wind slab may remain on lee N through SE slopes near and above treeline, but should generally be stubborn to human triggering. Firm wind transported snow and snowpack cracking can be good signs of wind slab layers.
Loose wet avalanches will be possible on steeper solar slopes, especially if there are prolonged periods of sunshine. Be aware of terrain traps where even a small loose avalanche could have unintended consequences in the wrong terrain.   Â
Recently formed cornices have grown large. If traveling along ridgelines, be aware that cornices break much further back than expected and you don't want to go for a ride with a chunk of cornice. Despite the recent cool weather, cornice releases can be unpredictable during the spring.
Snowpack Discussion
Weather and Snowpack
A low pressure system crossed the Northwest on Monday and Tuesday. NWAC stations at Mt. Hood accumulated a few inches above 4000 feet during this time. Light rain was seen on Wednesday afternoon in the below treeline band before a cold front swept through Wednesday night with moderate to strong westerly transport winds continuing through early Friday morning.
Post-frontal snow accumulations Wednesday night through Friday morning varied based on elevation, with only a few inches below 5000 feet and about 8-10 inches at the Mt. Hood Meadows and Timberline stations.Â
Frequent March storms have built large cornices along ridges in many areas.
The mid and lower snowpack along the west slopes should generally be a stable mix of crusts and layers of moist and rounded snow crystals.
Recent Observations
The Mt Hood Meadows pro-patrol on Tuesday morning 3/22 found wind loaded pockets of mostly small wind slab 12-18 inches deep in the above tree line which were stubborn to release by skis. On Tuesday afternoon a recent natural cornice release was seen at about 7000 feet on Marmot Ridge which released a small pocket of wind slab.
By Wednesday morning, Meadows pro-patrol found dense wind slab above treeline and on lee slopes only affected by large explosives. Above treeline, satstrugi was widely sculpted into the snow surface with some icy surfaces on windward ridges. Â
Avalanche Problems
Loose Wet
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: East, South East, South, South West, West.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 1
Wind Slabs
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: North, North East, East, South East.
Elevations: Alpine, Treeline.
Likelihood: Unlikely
Expected Size: 1 - 1