Avalanche Forecast
Regions: Mt Hood.
Winds slabs will be the primarily concern Saturday with westerly aspects receiving new wind loading but other aspects may be cross-loaded as well. Careful route finding and attention to local loading patterns will be necessary to have a safe and enjoyable day in avalanche terrain especially above treeline.
Detailed Forecast
East winds will increase and become strong E-NE Friday night and continue significant loading of westerly aspects through most of Saturday.Â
Winds slabs will be the primarily concern Saturday, so pay attention to the local loading pattern in your area, but generally expect non-traditional westerly aspects to have significant wind loading. Some slopes may be cross-loaded by the shifting winds over the life of the storm.  Â
Lesser avalanche problems that are still possible are storm slabs where storm instabilities persist in wind sheltered terrain and loose wet avalanches on steeper solar slopes. The sun is strong enough at the end of February to activate loose wet avalanches even on cooler days.Â
Due to the low snowpack, especially below treeline, watch for terrain hazards such as open creeks, partially covered rocks and vegetation. Many areas below treeline do not have enough snow (new or existing) to pose an avalanche hazard.Â
Snowpack Discussion
Since the wet start to February, fair weather through mid-February has led to generally thick surface crusts, as well as further deterioration of the snow cover below treeline. Weak weather disturbances passed through in NW flow aloft last week producing light snowfall but no new avalanche concerns.Â
New snowfall at NWAC Mt. Hood stations from Wednesday night through Thursday afternoon ranged from less than 1 inch at Meadows to a soggy 3 inches at Timberline with likely higher accumulations and some loading of easterly aspects above treeline.Â
A low pressure system brought variable amounts of new snow to Mt. Hood on Friday, with Timberline base station receiving roughly 6 inches during the day but Mt. Hood Meadows base only receiving a few inches. Still this was enough to build sensitive new wind slab Friday morning at about 6600 ft on a NE aspect at Meadows, with soft wind slabs around 1 ft easily releasing.Â
The mid and lower snowpack at Mt Hood snow consist of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.
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, 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: South East, South, South West, West.
Elevations: Alpine, Treeline.
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, Treeline.
Likelihood: Unlikely
Expected Size: 1 - 1