Avalanche Forecast
Regions: Mt Hood.
Use caution in higher elevations where possibly greater new snow may accumulate, especially lee slopes near ridges. Watch for areas of wet snow at mid elevations, and during daytime warming.
Detailed Forecast
A frontal passage Friday night should cause some light to moderate new snow, but initially rain changing to snow should leave good bonding of new snow to the old wet snow surface.
Update Saturday morning: Wind slab has been added to the above treeline forecast for the Cascade west slopes and Mt Hood due to stronger than expected winds and greater than expected snow. But the cooling trend seen Friday night should also help limit new instability in many areas
Watch for areas where new snow has been transported by wind to lee slopes at higher elevations along ridges. Also, watch for cornice development that may be soft and sensitive to trigger or release from daytime warming.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
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 of 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 and again Friday 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
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.
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: North, North East, East, South East, North West.
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: Possible
Expected Size: 1 - 1