Avalanche Forecast
Regions: Mt Hood.
The snowpack may remain reactive and dangerous on Saturday and is only beginning the spring stabilizing process. Backcountry travel in avalanche terrain above treeline is not recommended on Saturday. Careful snowpack evaluation and cautious routefinding will be required in other areas.
Detailed Forecast
Another front will cross the Northwest on Saturday. This will bring another day of increasing strong alpine winds and increasing rain or snow to the Olympics and Cascades. Snow levels should rise up to about 6000 feet at Mt Hood.
Wind slab should be suspected mainly above treeline on all aspects but is most likely on NW to SE aspects due to recent SW to W winds. Watch for firmer wind transported snow on varied aspects especially in areas of complex terrain.
New sensitive storm slab is most likely above treeline in areas that receive more than a few inches of rapidly accumulating snowfall.
Avoid travel on ridges near where cornices may have formed and avoid steep slopes below cornices that may fail at any time. Cornices have been reported as large in many areas. They will have been loaded and weakened during the recent storms.
Further loose wet avalanches are most likely in the near and below treeline due to rain that should affect those areas.
Although not listed as an avalanche problem wet slab avalanches are possible in areas that receive significant rain on Saturday.
The snowpack may remain reactive and dangerous on Saturday and is only beginning the spring stabilizing process. Higher precipitation intensities could trigger avalanches. Avalanches may step down or entrain deeper layers and be large and dangerous especially if they reach the Valentine's Day crust layer.
 Backcountry travel in avalanche terrain above treeline is not recommended on Saturday. Careful snowpack evaluation and cautious routefinding will be required in other areas.
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Snowpack Discussion
Weather and Snowpack
The first week or so of March was very cool and snowy. NWAC stations at Mt Hood piled up about 6-7 ft of snow.
A strong frontal system brought increasing precipitation and winds along with a warming trend to the Cascades on Thursday. On Thursday night rain pushed up to about 7000 feet at Mt Hood. By Friday morning NWAC stations at Mt Hood had about 1.6 in of WE but alas only rain to show for it.
This caused an avalanche cycle at Mt Hood. The snow and avalanche conditions are rapidly changing in the Cascades!
Recent Observations
The Meadows patrol on Thursday reported that rainfall was saturating the upper snowpack allowing several feet of boot penetration by mid-day.
NWAC observer Laura Green was out on Friday and reported new large cornice triggered slab avalanches in White River Canyon on SE aspects in the 6500-8500 ft range, and in Heather Canyon on a NE aspect in the 6100-6800 ft range. Very large debris was seen from new avalanches in Newton Canyon. Laura reports that in the 5200-6600 ft range the upper snowpack of 4F wet and some lower density drier layers.
Avalanche Problems
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: All aspects.
Elevations: Alpine.
Likelihood: Very Likely
Expected Size: 1 - 1
Storm Slabs
Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. Storm-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.
You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.
Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.
Aspects: All aspects.
Elevations: Alpine.
Likelihood: Likely
Expected Size: 1 - 1
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind lips of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
Cornices can never be trusted and avoiding them is necessary for safe backcountry travel. Stay well back from ridgeline areas with cornices. They often overhang the ridge edge can be triggered remotely. Avoid areas underneath cornices. Even small Cornice Fall can trigger a larger avalanche and large Cornice Fall can easily crush a human. Periods of significant temperature warm-up are times to be particularly aware.
A corniced ridgeline. A large cornice has formed at the top of the ridge. A smaller cornice has formed to the left of the trees from crossloading.
Cornices are easy to identify and are confined to lee and cross-loaded ridges, sub-ridges, and sharp convexities. They are easiest to trigger during periods of rapid growth (new snow and wind), rapid warming, and during rain-on-snow events. Cornices often catch people by surprise when they break farther back onto flatter areas than expected.
Aspects: North, North East, East, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 2
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.
Elevations: Treeline, Below Treeline.
Likelihood: Likely
Expected Size: 1 - 1