Avalanche Forecast
Regions: Mt Hood.
Moist to wet surface snow should maintain loose wet snow avalanche potential Friday. Also, watch for recent cornice development along ridges.
Detailed Forecast
Increasing high clouds, but warm temperatures are expected for Mt. Hood Friday with high freezing levels that will gradually lower late Friday. This should maintain the possibility of loose wet avalanches, especially on solar slopes near and above treeline that did not naturally avalanche Wednesday or Thursday.
Avoid steeper slopes if you are sinking in more than a few inches, and be aware the even small loose wet avalanches are powerful and can push you into unintended terrain features. Â
Fresh cornices along ridgelines have likely been weakened and should become susceptible to failure again Friday under warm weather and potential sunshine. Make sure to give them a wide berth, and be aware of corniced slopes above you. Â
Less recent snow and ample terrain anchors may limit the avalanche danger below treeline. Many areas at the lowest elevations do not have enough snow to cause an avalanche danger.
Snowpack Discussion
About 4-6 inches of snow was seen above about 6000 feet Saturday building some stubborn wind slab up to 1 foot on lee NE slopes as noted my the Meadows pro patrol.Â
A fairly vigorous low pressure system moved east over the Mt Hood area Monday night/Tuesday morning offering a taste of winter-like conditions; new snow amounts were about 9-11 inches at Mt Hood. On Tuesday, the Meadows patrol only ventured up to 6600 feet due to stormy conditions where they found lee slopes and start zones loading and pockets of 6-10 inch wind slab triggered by ski cuts and explosives. Those same lee slopes at 6600 feet on Wednesday AM produced pockets on wind slab that did not readily propagate along with some sensitive cornices.
Light to moderate precipitation along with a warming trend tapered off Wednesday afternoon as snow levels pushed above 7000 feet.
Sunny and very warm temperatures Thursday helped to melt and weaken surface snow layers, however, no avalanches have been reported thus far. Â
Snowpack problems at Mt Hood for the time being should be in the upper or surface layers. The mid and lower snowpack at Mt Hood consists of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter. The snowpack at low elevations at Mt Hood remains meager to non-existent.
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: Alpine, Treeline.
Likelihood: Possible
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 - 1