Avalanche Forecast
Regions: Mt Hood.
Don't underestimate the effects of the strong April sun, which can make avalanches touchy Sunday, especially in areas of heavier storm snowfall.
Detailed Forecast
High pressure should begin building into the Pacific Northwest Sunday, causing clearing and slow warming. Temperatures should be cool early Sunday with only a moderate rise in freezing levels by afternoon. This should allow for recent snow over the past few days to settle.Â
The main avalanche problems Sunday should shift from any recent storm or wind slab to mainly loose wet avalanches on slopes receiving sunshine and during the afternoon in areas with sufficient snowcover for avalanches.Â
Watch for wet surface snow that gets deeper than a few inches, pinwheels or initial small natural avalanches from rocks or cliffs that are signs to shift to lower angle slopes.
Cornices won't be listed as an avalanche problem, but avoid slopes below cornices and areas on the ridge where it may be difficult to know if a cornice is present.
Remember that this forecast applies to elevations up to the Cascade crest and does not apply to higher elevations on the volcanoes where conditions at this time of year are often more dangerous.
The mid and lower snowpack is most areas should consist of stable rounded grains and crust from warm periods this winter.
The work of the 3Â NWAC forecasters is transitioning to other essential parts of the program before the NWAC closes for the summer.
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Snowpack Discussion
After a cool, snowy start in early April, mid April provided about a week of warm dry weather. This caused loose wet snow avalanches and consolidation. Layers from early April have stabilized, making any avalanche activity confined to new snow received over the past few days.
A cold front moved across the Northwest on Thursday. The front was followed by a low pressure system, south to southwest winds and a cool unstable air mass that caused snow showers at low freezing levels Friday and Saturday. Storm snow amounts have been highly variable under the showery recent weather pattern. As of Saturday afternoon, about 8-14 inches of new snow have been received since Thursday on Mt Hood.  The new snow has already begun to settle Saturday afternoon under daytime warming.
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Avalanche Problems
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.
Elevations: Below Treeline.
Likelihood: Possible
Expected Size: 1 - 1
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: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1