Avalanche Forecast
Regions: Mt Hood.
The main avalanche problem at Mt Hood should be possible small loose wet avalanches on solar slopes. But isolated storm slab may still be found on slopes mainly above treeline where there has been recent heavier snow showers.
Detailed Forecast
The weak shortwave, moisture and instability should continue to linger over Washington on Thursday. So expect cumulus and a slight chance of showers will be forecast again Thursday afternoon mainly over the central and south Cascades.
It's April, so be aware of the increased sun effects reaching more aspects and affecting the snow surface fairly quickly. Loose wet avalanches involving shallow amounts of recent storm snow will be possible Thursday, especially in any direct sun on solar slopes.
Most storm slab should be stabilized by Thursday. But continue to watch for storm slab layers where storm snow instabilities may have formed during snow showers or where recent snow seems poorly bonded to underlying crusts.
Cornices won't be highlighted as an avalanche problem due to the cool weather but use caution on slopes below cornices and on ridges where it can be hard to know if a cornice is present.
Snowpack Discussion
A front caused moderate west winds and 1-3 inches of new snow at NWAC stations on Mt. Hood Friday night, with some moderate westerly wind transport above treeline. But the Meadows patrol reported only isolated pockets of wind slab up to 1 foot above treeline on lee aspects over the weekend.
A large weak upper trough moved over the Northwest last weekend through early this week. The main showers at Mt Hood were Sunday when NWAC stations at Mt Hood had 6-7 inches. Freezing levels have been very low in April compared to most of the winter, averaging about 4-5000 feet. Shallow 4 inch potential storm slab layers was reported by the Meadows patrol Monday.
A weak shortwave, moisture and instability is causing cumulus and showers Wednesday mainly over the central and south Cascades. The Meadows patrol reports easy shears in quick test pits in recent snow at 7300 feet on Wednesday.
Snowpack problems at Mt Hood should remain 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 season. Many areas at low elevations do not have enough snow to cause an avalanche danger.
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
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: Possible
Expected Size: 1 - 1