Avalanche Forecast
Regions: Mt Hood.
Be wary of unstable layers created during periods of rapid accumulation Monday that would make wind or storm slabs more likely to trigger. Persistent SW-W winds will continue to load lee slopes above treeline. Overall the potential for loose wet avalanches will decrease Monday and be confined to the lower elevations of the below treeline band and to steeper solar aspects that receive sunbreaks.
Detailed Forecast
Light to locally moderate new snow received through Monday afternoon should accumulate at relatively cool and stable snow levels.Â
Be wary of unstable layers created during periods of rapid accumulation Monday that would make wind or storm slabs more likely to trigger. Persistent SW-W winds will continue to load lee slopes above treeline. Overall the potential for loose wet avalanches will decrease Monday and be confined to the lower elevations of the below treeline band and to steeper solar aspects that receive sunbreaks.Â
Cornices formed over the last week may still be weak from the recent mild weather so be aware of the overhead hazard and give cornices a wide berth while traveling along ridgelines.Â
Â
Snowpack Discussion
Weather and Snowpack
The last week has been wet and relatively mild with a series of active fronts transiting the region resulting in fluctuating freezing levels and periods of very strong winds (100+ mph gusts were not uncommon at the Cascade Express station).
The latter half of the week including the weekend has featured more rain than snow at NWAC sites on Mt. Hood. For perspective, the averaged freezing level measured in March thus far has been 6600 ft at Salem; more akin to spring than late winter. Â
The mid and lower snow pack along the west slopes should be a stable mix of crusts and layers of moist and rounded snow crystals.
Recent Observations
The aftermath of the extreme wind event Tuesday was seen on Wednesday, with any exposed terrain stripped of recent snow, exposing a strong crust. The wind deposits were inconsistent and did not yield much in the way of avalanches, despite a healthy dose of bombs in the Mt Hood Meadows area.Â
On Saturday, Mt. Hood Meadows pro-patrol reported wet snow up to about 6600' with a thin crust above and a well consolidated snowpack in their area. Following the cool down Saturday night, pockets of shallow new wind slab were seen above treeline in the Mt. Hood Meadows area by early Sunday morning.Â
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
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: All elevations.
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.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 1