Avalanche Forecast
Regions: Mt Hood.
Generally good stability is expected Sunday, but evaluate lee slopes near and above treeline for local wind slab and be aware of small loose avalanches that could be problematic near terrain traps.
Detailed Forecast
Another day of weak flow aloft and cool snow levels with mainly afternoon/evening shower activity is expected Sunday.  New snow amounts are expected to be light Saturday night and Sunday.   Â
There haven't been many reports of wind slab, but isolated pockets of wind slab may linger on traditional lee westerly aspects from recent storms near and above treeline. Â
It's April, so be aware of increased solar input reaching more aspects and affecting the snow surface more quickly than winter-time. Loose wet avalanches involving recent storm snow will be possible if there are sunbreaks Sunday.Â
Small loose dry avalanches are also possible on non-solar aspects. Loose dry avalanches won't be listed as a top avalanche problem, but be aware of fast moving sluffs knocking you off your feet and into unintended terrain traps on steeper slopes.Â
Due to the continued cool weather, cornices won't be listed as an avalanche problem either but use caution on slopes below cornices and on ridges where it can be hard to know if a cornice is present.
Snowpack Discussion
Periods of active weather and mountain snowfall have finally been graced the PNW since about mid March onward. Snowfall during this period was limited near and below treeline at Mt Hood but more significant above treeline.Â
A front moved across the Northwest Tuesday followed by showers and rapid cooling Tuesday night and Wednesday. Storm snow from this system was about 9-15 inches at Mt Hood. The patrol at Meadows on Wednesday reported that the storm snow was surprisingly less reactive than anticipated. The storm snow produced some 6-12 inch loose dry and very soft storm slab avalanches from explosive control with no ski triggered avalanches.
Cool and dry weather was seen Thursday and much of Friday. The Meadows patrol reported no avalanches with firm snow or surface snow getting heavy on solar slopes and staying cool on north slopes. 1-3" of new snow fell at Mt. Hood stations Friday night with some moderate westerly wind transport above treeline, potentially building new shallow and soft wind slab. Â
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
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: 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: Unlikely
Expected Size: 1 - 1