Avalanche Forecast
Regions: Mt Hood.
A variety of avalanche problems on Thursday will present dangerous conditions in all elevation bands at Mt. Hood. If you venture out Thursday, use conservative decision making and terrain selection.
Detailed Forecast
Mt. Hood should be in the warm sector Thursday with a frontal system stalled offshore. Precipitation amounts look rather paltry for this neck of the woods, but snow levels should begin to rise Wednesday night and continue on Thursday with sustained S-SW winds. Â
Deep wind slab built Tuesday and Wednesday should most likely be found on lee north to southeast slopes near and above treeline, but watch for locally cross-loaded slopes. Wind slabs may have grown very large over the past few days... and although fairly unlikely to naturally release or to be responsive to human triggering, would lead to a large and deadly slide. Â
Storm slabs may still be sensitive to human triggering on Thursday, so choose more moderate slopes if you find lingering storm snow instabilities.Â
Loose wet avalanches will become likely due to light rain and rising freezing levels. Loose wet avalanches should be small and confined to steeper slopes near and below treeline. Be especially wary near terrain traps, where even a small avalanche could have unintended consequences.Â
A variety of avalanche problems on Thursday will present dangerous conditions in all elevation bands at Mt. Hood. If you venture out Thursday, use conservative decision making and terrain selection relative to the avalanche problem.Â
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Snowpack Discussion
A continuous period of active weather for about the past week has brought several feet of snow to NWAC stations at Mt Hood. Fluctuating snow levels over this period has occasionally mixed rain up into the near treeline elevation band during this storm cycle.
Most recently, roughly 2 feet of new snow accumulated Tuesday and Tuesday night at Timberline and Meadows NWAC base stations with consistent westerly transport winds buffeting the near and above treeline that continued through Wednesday afternoon. Â
Limited small wind slab avalanches to 14 inches on northeast slopes above tree line via avalanche control were reported by the Mt Hood Meadows pro patrol through Tuesday afternoon.
However, Meadows pro-patrol reported a much more active day on Wednesday with all the new snow. Storm and wind slab releases, mostly initiated with explosives but also sensitive to ski cutting, ranged from 1 to 3 feet, with the larger slabs on lee aspects near and above treeline. Wind affects were seen into the below treeline band, and also allowed hard slabs to form on lee slopes higher in the terrain. Debris from a natural avalanche was observed in White River Canyon at around 8000'.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 - 2
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: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 1